Pyrrolobenzodiazepine-antibody conjugates

ABSTRACT

Conjugates of specific PBD dimers with an antibody that binds to PSMA, the antibody comprising a VH domain having the sequence according to any one of SEQ ID NOs. 1, 3, 5, 7, 8, 9, or 10, optionally further comprising a VL domain having the sequence 5 according to any one of SEQ ID NOs. 2, 4, 6, 11, 12, 13, 14, 15, 16, 17, or 18.

The present invention relates to pyrrolobenzodiazepines (PBDs) having a labile protecting group in the form of a linker to an antibody.

BACKGROUND TO THE INVENTION

Pyrrolobenzodiazepines

Some pyrrolobenzodiazepines (PBDs) have the ability to recognise and bond to specific sequences of DNA; the preferred sequence is PuGPu. The first PBD antitumour antibiotic, anthramycin, was discovered in 1965 (Leimgruber, et al., J. Am. Chem. Soc., 87, 5793-5795 (1965); Leimgruber, et al., J. Am. Chem. Soc., 87, 5791-5793 (1965)). Since then, a number of naturally occurring PBDs have been reported, and over 10 synthetic routes have been developed to a variety of analogues (Thurston, et al., Chem. Rev. 1994, 433-465 (1994); Antonow, D. and Thurston, D. E., Chem. Rev. 2011 111 (4), 2815-2864). Family members include abbeymycin (Hochlowski, et al., J. Antibiotics, 40, 145-148 (1987)), chicamycin (Konishi, et al., J. Antibiotics, 37, 200-206 (1984)), DC-81 (Japanese Patent 58-180 487; Thurston, et al., Chem. Brit., 26, 767-772 (1990); Bose, et al., Tetrahedron, 48, 751-758 (1992)), mazethramycin (Kuminoto, et al., J. Antibiotics, 33, 665-667 (1980)), neothramycins A and B (Takeuchi, et al., J. Antibiotics, 29, 93-96 (1976)), porothramycin (Tsunakawa, et al., J. Antibiotics, 41, 1366-1373 (1988)), prothracarcin (Shimizu, et al, J. Antibiotics, 29, 2492-2503 (1982); Langley and Thurston, J. Org. Chem., 52, 91-97 (1987)), sibanomicin (DC-102)(Hara, et al., J. Antibiotics, 41, 702-704 (1988); Itoh, et al., J. Antibiotics, 41, 1281-1284 (1988)), sibiromycin (Leber, et al., J. Am. Chem. Soc., 110, 2992-2993 (1988)) and tomamycin (Arima, et al., J. Antibiotics, 25, 437-444 (1972)). PBDs are of the general structure:

They differ in the number, type and position of substituents, in both their aromatic A rings and pyrrolo C rings, and in the degree of saturation of the C ring. In the B-ring there is either an imine (N═C), a carbinolamine(NH—CH(OH)), or a carbinolamine methyl ether (NH—CH(OMe)) at the N10-C11 position which is the electrophilic centre responsible for alkylating DNA. All of the known natural products have an (S)-configuration at the chiral C11a position which provides them with a right-handed twist when viewed from the C ring towards the A ring. This gives them the appropriate three-dimensional shape for isohelicity with the minor groove of B-form DNA, leading to a snug fit at the binding site (Kohn, In Antibiotics III. Springer-Verlag, New York, pp. 3-11 (1975); Hurley and Needham-VanDevanter, Acc. Chem. Res., 19, 230-237 (1986)). Their ability to form an adduct in the minor groove, enables them to interfere with DNA processing, hence their use as antitumour agents.

One pyrrolobenzodiazepine compound is described by Gregson et al. (Chem. Commun. 1999, 797-798) as compound 1, and by Gregson et al. (J. Med. Chem. 2001, 44, 1161-1174) as compound 4a. This compound, also known as SG2000, is shown below:

WO 2007/085930 describes the preparation of dimer PBD compounds having linker groups for connection to a cell binding agent, such as an antibody. The linker is present in the bridge linking the monomer PBD units of the dimer.

Dimer PBD compounds having linker groups for connection to a cell binding agent, such as an antibody, have been described in WO 2011/130613 and WO 2011/130616. The linker in these compounds is attached to the PBD core via the C2 position, and are generally cleaved by action of an enzyme on the linker group. In WO 2011/130598, the linker in these compounds is attached to one of the available N10 positions on the PBD core, and are generally cleaved by action of an enzyme on the linker group.

Antibody-drug Conjugates

Antibody therapy has been established for the targeted treatment of patients with cancer, immunological and angiogenic disorders (Carter, P. (2006) Nature Reviews Immunology 6:343-357). The use of antibody-drug conjugates (ADC), i.e. immunoconjugates, for the local delivery of cytotoxic or cytostatic agents, i.e. drugs to kill or inhibit tumor cells in the treatment of cancer, targets delivery of the drug moiety to tumors, and intracellular accumulation therein, whereas systemic administration of these unconjugated drug agents may result in unacceptable levels of toxicity to normal cells (Xie et al (2006) Expert. Opin. Biol. Ther. 6(3):281-291; Kovtun et al (2006) Cancer Res. 66(6):3214-3121; Law et al (2006) Cancer Res. 66(4):2328-2337; Wu et al (2005) Nature Biotech. 23(9):1137-1145; Lambert J. (2005) Current Opin. in Pharmacol. 5:543-549; Hamann P. (2005) Expert Opin. Ther. Patents 15(9):1087-1103; Payne, G. (2003) Cancer Cell 3:207-212; Trail et al (2003) Cancer Immunol. Immunother. 52:328-337; Syrigos and Epenetos (1999) Anticancer Research 19:605-614).

Maximal efficacy with minimal toxicity is sought thereby. Efforts to design and refine ADC have focused on the selectivity of monoclonal antibodies (mAbs) as well as drug mechanism of action, drug-linking, drug/antibody ratio (loading), and drug-releasing properties (Junutula, et al., 2008b Nature Biotech., 26(8):925-932; Dornan et al (2009) Blood 114(13):2721-2729; U.S. Pat. No. 7,521,541; U.S. Pat. No. 7,723,485; WO2009/052249; McDonagh (2006) Protein Eng. Design & Sel. 19(7): 299-307; Doronina et al (2006) Bioconj. Chem. 17:114-124; Erickson et al (2006) Cancer Res. 66(8):1-8; Sanderson et al (2005) Clin. Cancer Res. 11:843-852; Jeffrey et al (2005) J. Med. Chem. 48:1344-1358; Hamblett et al (2004) Clin. Cancer Res. 10:7063-7070). Drug moieties may impart their cytotoxic and cytostatic effects by mechanisms including tubulin binding, DNA binding, proteasome and/or topoisomerase inhibition. Some cytotoxic drugs tend to be inactive or less active when conjugated to large antibodies or protein receptor ligands.

The present inventors have developed particular PBD dimer antibody conjugates.

SUMMARY OF THE INVENTION

A first aspect of the present invention provides a conjugate of formula ConjA:

ConjB:

ConjC

or

ConjDE:

where Ab represents an antibody as defined below. The link to the moiety shown is via a free S (active thiol) on the cell binding agent.

A second aspect of the invention provides a method of making a conjugate according to the first aspect of the invention comprising conjugating a compound which is selected from A:

B:

C:

D:

and

E:

with an antibody as defined below.

WO 2010/043380 and WO 2011/130613 disclose compound 30:

WO 2011/130613 also discloses compound 51:

Compound A differs from compound 30 by only having a (CH₂)₃ tether between the PBD moieties, instead of a (CH₂)₅ tether, which reduces the lipophilicity of the released PBD dimer. The linking group in both Compounds A and B is attached to the C2-phenyl group in the para rather than meta position.

Compounds C, D and E differ from previously disclosed PBD dimers with a drug linker having a C2-3 endo-double bond, by having a smaller, less lipophilic C2 substituent, e.g. 4F-phenyl, propylene. As such, the conjugates of compounds C, D and E are less likely to aggregate once synthesised. Such aggregation of conjugates can be measured by Size exclusion chromatography (SEC).

Compound C has a cleavable protecting group on the second imine group which avoids cross-reactions during its synthesis and in the final product avoids the formation of carbinolamine and carbinolamine methyl ethers. This protection also avoids the presence of a reactive imine group in the molecule.

Compounds D and E comprise an iodoacetamide and bormoacetamide groups respectively for linking to the cell binding agent.

All five compounds have two sp² centres in each C-ring, which may allow for stronger binding in the minor groove of DNA, than for compounds with only one sp² centre in each C-ring.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a PBD dimer with a linker connected through the C2 or N10 position on one of the PBD moieties conjugated to an antibody as defined below.

The present invention is suitable for use in providing a PBD compound to a preferred site in a subject. The conjugate allows the release of an active PBD compound that does not retain any part of the linker. There is no stub present that could affect the reactivity of the PBD compound. Thus ConjA would release the compound RelA:

ConjB would release the compound RelB:

and

ConjC and ConjDE would release the compound RelC:

The specified link between the PBD dimer and the cell binding agent, e.g. antibody, in the present invention is preferably stable extracellularly. Before transport or delivery into a cell, the antibody-drug conjugate (ADC) is preferably stable and remains intact, i.e. the antibody remains linked to the drug moiety. The linkers are stable outside the target cell and may be cleaved at some efficacious rate inside the cell. An effective linker will: (i) maintain the specific binding properties of the antibody; (ii) allow intracellular delivery of the conjugate or drug moiety; (iii) remain stable and intact, i.e. not cleaved, until the conjugate has been delivered or transported to its targetted site; and (iv) maintain a cytotoxic, cell-killing effect or a cytostatic effect of the PBD drug moiety. Stability of the ADC may be measured by standard analytical techniques such as mass spectroscopy, HPLC, and the separation/analysis technique LC/MS.

Delivery of the compounds of formulae RelA, RelB, or RelC is achieved at the desired activation site of the conjugates of formulae ConjA, ConjB, ConjC or ConjDE by the action of an enzyme, such as cathepsin, on the linking group, and in particular on the valine-alanine dipeptide moiety.

Antibody

In one aspect the antibody is in one aspect the antibody is an antibody that binds to PSMA, the antibody comprising a VH domain having the sequence according to any one of SEQ ID NOs. 1, 3, 5, 7, 8, 9, or 10.

The antibody may further comprise a VL domain. In some embodiments the antibody further comprises a VL domain having the sequence according to any one of SEQ ID NOs. 2, 4, 6, 11, 12, 13, 14, 15, 16, 17, or 18.

In some embodiments the antibody comprises a VH domain paired with a VL domain, the VH and VL domains having sequences selected from the group consisting of:

-   -   SEQ ID NO. 1 paired with any one of SEQ ID NOs. 2, 4, 6, 11, 12,         13, 14, 15, 16, 17, or 18;     -   SEQ ID NO. 3 paired with any one of SEQ ID NOs. 2, 4, 6, 11, 12,         13, 14, 15, 16, 17, or 18;     -   SEQ ID NO. 5 paired with any one of SEQ ID NOs. 2, 4, 6, 11, 12,         13, 14, 15, 16, 17, or 18;     -   SEQ ID NO. 7 paired with any one of SEQ ID NOs. 2, 4, 6, 11, 12,         13, 14, 15, 16, 17, or 18; SEQ ID NO. 8 paired with any one of         SEQ ID NOs. 2, 4, 6, 11, 12, 13, 14, 15, 16, 17, or 18;     -   SEQ ID NO. 9 paired with any one of SEQ ID NOs. 2, 4, 6, 11, 12,         13, 14, 15, 16, 17, or 18; or     -   SEQ ID NO. 10 paired with any one of SEQ ID NOs. 2, 4, 6, 11,         12, 13, 14, 15, 16, 17, or 18. For example SEQ ID NO. 1 paired         with SEQ ID NO. 2, SEQ ID NO. 3 paired with SEQ ID NO. 4, SEQ ID         NO. 5 paired with SEQ ID NO. 6, SEQ ID NO. 7 paired with SEQ ID         NO. 11, SEQ ID NO. 7 paired with SEQ ID NO. 12, SEQ ID NO. 7         paired with SEQ ID NO. 13, SEQ ID NO. 7 paired with SEQ ID NO.         14, SEQ ID NO. 7 paired with SEQ ID NO. 15, SEQ ID NO. 7 paired         with SEQ ID NO. 16, SEQ ID NO. 7 paired with SEQ ID NO. 17, SEQ         ID NO. 7 paired with SEQ ID NO. 18, SEQ ID NO. 8 paired with SEQ         ID NO. 11, SEQ ID NO. 8 paired with SEQ ID NO. 12, SEQ ID NO. 8         paired with SEQ ID NO. 13, SEQ ID NO. 8 paired with SEQ ID NO.         14, SEQ ID NO. 8 paired with SEQ ID NO. 15, SEQ ID NO. 8 paired         with SEQ ID NO. 16, SEQ ID NO. 8 paired with SEQ ID NO. 17, SEQ         ID NO. 8 paired with SEQ ID NO. 18, SEQ ID NO. 9 paired with SEQ         ID NO. 11, SEQ ID NO. 9 paired with SEQ ID NO. 12, SEQ ID NO. 9         paired with SEQ ID NO. 13, SEQ ID NO. 9 paired with SEQ ID NO.         14, SEQ ID NO. 9 paired with SEQ ID NO. 15, SEQ ID NO. 9 paired         with SEQ ID NO. 16, SEQ ID NO. 9 paired with SEQ ID NO. 17, SEQ         ID NO. 9 paired with SEQ ID NO. 18, SEQ ID NO. 10 paired with         SEQ ID NO. 11, SEQ ID NO. 10 paired with SEQ ID NO. 12, SEQ ID         NO. 10 paired with SEQ ID NO. 13, SEQ ID NO. 10 paired with SEQ         ID NO. 14, SEQ ID NO. 10 paired with SEQ ID NO. 15, SEQ ID NO.         10 paired with SEQ ID NO. 16, SEQ ID NO. 10 paired with SEQ ID         NO. 17, or SEQ ID NO. 10 paired with SEQ ID NO. 18.

The VH and VL domain(s) may pair so as to form an antibody antigen binding site that binds PSMA.

In some embodiments the antibody is an intact antibody comprising a VH domain paired with a VL domain, the VH and VL domains having sequences selected from the group consisting of:

-   -   SEQ ID NO. 1 paired with any one of SEQ ID NOs. 2, 4, 6, 11, 12,         13, 14, 15, 16, 17, or 18;     -   SEQ ID NO. 3 paired with any one of SEQ ID NOs. 2, 4, 6, 11, 12,         13, 14, 15, 16, 17, or 18;     -   SEQ ID NO. 5 paired with any one of SEQ ID NOs. 2, 4, 6, 11, 12,         13, 14, 15, 16, 17, or 18;     -   SEQ ID NO. 7 paired with any one of SEQ ID NOs. 2, 4, 6, 11, 12,         13, 14, 15, 16, 17, or 18;     -   SEQ ID NO. 8 paired with any one of SEQ ID NOs. 2, 4, 6, 11, 12,         13, 14, 15, 16, 17, or 18;     -   SEQ ID NO. 9 paired with any one of SEQ ID NOs. 2, 4, 6, 11, 12,         13, 14, 15, 16, 17, or 18; or     -   SEQ ID NO. 10 paired with any one of SEQ ID NOs. 2, 4, 6, 11,         12, 13, 14, 15, 16, 17, or 18. For example SEQ ID NO. 1 paired         with SEQ ID NO. 2, SEQ ID NO. 3 paired with SEQ ID NO. 4, SEQ ID         NO. 5 paired with SEQ ID NO. 6, SEQ ID NO. 7 paired with SEQ ID         NO. 11, SEQ ID NO. 7 paired with SEQ ID NO. 12, SEQ ID NO. 7         paired with SEQ ID NO. 13, SEQ ID NO. 7 paired with SEQ ID NO.         14, SEQ ID NO. 7 paired with SEQ ID NO. 15, SEQ ID NO. 7 paired         with SEQ ID NO. 16, SEQ ID NO. 7 paired with SEQ ID NO. 17, SEQ         ID NO. 7 paired with SEQ ID NO. 18, SEQ ID NO. 8 paired with SEQ         ID NO. 11, SEQ ID NO. 8 paired with SEQ ID NO. 12, SEQ ID NO. 8         paired with SEQ ID NO. 13, SEQ ID NO. 8 paired with SEQ ID NO.         14, SEQ ID NO. 8 paired with SEQ ID NO. 15, SEQ ID NO. 8 paired         with SEQ ID NO. 16, SEQ ID NO. 8 paired with SEQ ID NO. 17, SEQ         ID NO. 8 paired with SEQ ID NO. 18, SEQ ID NO. 9 paired with SEQ         ID NO. 11, SEQ ID NO. 9 paired with SEQ ID NO. 12, SEQ ID NO. 9         paired with SEQ ID NO. 13, SEQ ID NO. 9 paired with SEQ ID NO.         14, SEQ ID NO. 9 paired with SEQ ID NO. 15, SEQ ID NO. 9 paired         with SEQ ID NO. 16, SEQ ID NO. 9 paired with SEQ ID NO. 17, SEQ         ID NO. 9 paired with SEQ ID NO. 18, SEQ ID NO. 10 paired with         SEQ ID NO. 11, SEQ ID NO. 10 paired with SEQ ID NO. 12, SEQ ID         NO. 10 paired with SEQ ID NO. 13, SEQ ID NO. 10 paired with SEQ         ID NO. 14, SEQ ID NO. 10 paired with SEQ ID NO. 15, SEQ ID NO.         10 paired with SEQ ID NO. 16, SEQ ID NO. 10 paired with SEQ ID         NO. 17, or SEQ ID NO. 10 paired with SEQ ID NO. 18.

In some embodiments, the antibody competes with the antibody secreted by hybridoma ATCC accession No. HB-12126 for binding to PSMA. In another aspect, the antibody competes with the antibody secreted by hybridoma ATCC accession No. HB-12109 for binding to PSMA. In one embodiment the antibody binds PSMA with an association constant (K_(a)) no less than 2, 5 or 10-fold less than the antibody secreted by the hybridoma.

In one aspect the antibody is the antibody secreted by a hydridoma. In one embodiment the hybridoma is ATCC accession No. HB-12126. In another embodiment the hybridoma is ATCC accession No. HB-12109.

In some embodiments the antibody is the J415 antibody disclosed in WO02/098897.

In some embodiments the antibody is the J519 antibody disclosed in WO02/098897.

In aspect the antibody is an antibody as described herein which has been modified (or further modified) as described below. In some embodiments the antibody is a humanised, deimmunised or resurfaced version of an antibody disclosed herein. For example, a humanised, deimmunised or resurfaced version of (i) the antibody comprising the VH domain SEQ ID NO. 1 paired with the VL domain SEQ ID NO. 2, (ii) the J519 antibody disclosed in WO02/098897, (iii) the antibody secreted by the hybridoma ATCC accession No. HB-12109, (iv) the antibody comprising the VH domain SEQ ID NO. 5 paired with the VL domain SEQ ID NO. 6, (v) the J415 antibody disclosed in WO02/098897, (vi) the antibody secreted by the hybridoma ATCC accession No. HB-12126.

Terminology

The term “antibody” herein is used in the broadest sense and specifically covers monoclonal antibodies, polyclonal antibodies, dimers, multimers, multispecific antibodies (e.g., bispecific antibodies), intact antibodies and antibody fragments, so long as they exhibit the desired biological activity, for example, the ability to bind PSMA (Miller et al (2003) Jour. of Immunology 170:4854-4861). Antibodies may be murine, human, humanized, chimeric, or derived from other species. An antibody is a protein generated by the immune system that is capable of recognizing and binding to a specific antigen. (Janeway, C., Travers, P., Walport, M., Shlomchik (2001) Immuno Biology, 5th Ed., Garland Publishing, New York). A target antigen generally has numerous binding sites, also called epitopes, recognized by CDRs on multiple antibodies. Each antibody that specifically binds to a different epitope has a different structure. Thus, one antigen may have more than one corresponding antibody. An antibody includes a full-length immunoglobulin molecule or an immunologically active portion of a full-length immunoglobulin molecule, i.e., a molecule that contains an antigen binding site that immunospecifically binds an antigen of a target of interest or part thereof, such targets including but not limited to, cancer cell or cells that produce autoimmune antibodies associated with an autoimmune disease. The immunoglobulin can be of any type (e.g. IgG, IgE, IgM, IgD, and IgA), class (e.g. IgG1, IgG2, IgG3, IgG4, IgA1 and IgA2) or subclass, or allotype (e.g. human G1m1, G1m2, G1m3, non-G1 m1 [that, is any allotype other than G1 m1], G1m17, G2m23, G3m21, G3m28, G3m11, G3m5, G3m13, G3m14, G3m10, G3m15, G3m16, G3m6, G3m24, G3m26, G3m27, A2 m1, A2m2, Km1, Km2 and Km3) of immunoglobulin molecule. The immunoglobulins can be derived from any species, including human, murine, or rabbit origin.

As used herein, “binds PSMA” is used to mean the antibody binds PSMA with a higher affinity than a non-specific partner such as Bovine Serum Albumin (BSA, Genbank accession no. CAA76847, version no. CAA76847.1 GI:3336842, record update date: Jan. 7, 2011 02:30 PM). In some embodiments the antibody binds PSMA with an association constant (K_(a)) at least 2, 3, 4, 5, 10, 20, 50, 100, 200, 500, 1000, 2000, 5000, 10⁴, 10⁵ or 10⁶-fold higher than the antibody's association constant for BSA, when measured at physiological conditions. The antibodies of the invention can bind PSMA with a high affinity. For example, in some embodiments the antibody can bind PSMA with a K_(D) equal to or less than about 10⁻⁶ M, such as 1×10⁻⁶, 10⁻⁷, 10⁻⁵, 10⁻⁹, 10⁻¹⁰, 10⁻¹¹, 10⁻¹², 10⁻¹³ or 10⁻¹⁴.

As used herein, PSMA refers to Prostate-Specific Membrane Antigen. In one embodiment, PSMA polypeptide corresponds to Genbank accession no. AAA60209, version no. AAA60209.1 GI:190664, record update date: Jun. 23, 2010 08:48 AM. In one embodiment, the nucleic acid encoding PSMA polypeptide corresponds to Genbank accession no. M99487, version no. M99487.1 GI:190663, record update date: Jun. 23, 2010 08:48 AM. “Antibody fragments” comprise a portion of a full length antibody, generally the antigen binding or variable region thereof. Examples of antibody fragments include Fab, Fab′, F(ab′)₂, and scFv fragments; diabodies; linear antibodies; fragments produced by a Fab expression library, anti-idiotypic (anti-Id) antibodies, CDR (complementary determining region), and epitope-binding fragments of any of the above which immunospecifically bind to cancer cell antigens, viral antigens or microbial antigens, single-chain antibody molecules; and multispecific antibodies formed from antibody fragments.

The term “monoclonal antibody” as used herein refers to an antibody obtained from a population of substantially homogeneous antibodies, i.e. the individual antibodies comprising the population are identical except for possible naturally occurring mutations that may be present in minor amounts. Monoclonal antibodies are highly specific, being directed against a single antigenic site. Furthermore, in contrast to polyclonal antibody preparations which include different antibodies directed against different determinants (epitopes), each monoclonal antibody is directed against a single determinant on the antigen. In addition to their specificity, the monoclonal antibodies are advantageous in that they may be synthesized uncontaminated by other antibodies. The modifier “monoclonal” indicates the character of the antibody as being obtained from a substantially homogeneous population of antibodies, and is not to be construed as requiring production of the antibody by any particular method. For example, the monoclonal antibodies to be used in accordance with the present invention may be made by the hybridoma method first described by Kohler et al (1975) Nature 256:495, or may be made by recombinant DNA methods (see, U.S. Pat. No. 4,816,567). The monoclonal antibodies may also be isolated from phage antibody libraries using the techniques described in Clackson et al (1991) Nature, 352:624-628; Marks et al (1991) J. Mol. Biol., 222:581-597 or from transgenic mice carrying a fully human immunoglobulin system (Lonberg (2008) Curr. Opinion 20(4):450-459).

The monoclonal antibodies herein specifically include “chimeric” antibodies in which a portion of the heavy and/or light chain is identical with or homologous to corresponding sequences in antibodies derived from a particular species or belonging to a particular antibody class or subclass, while the remainder of the chain(s) is identical with or homologous to corresponding sequences in antibodies derived from another species or belonging to another antibody class or subclass, as well as fragments of such antibodies, so long as they exhibit the desired biological activity (U.S. Pat. No. 4,816,567; and Morrison et al (1984) Proc. Natl. Acad. Sci. USA, 81:6851-6855). Chimeric antibodies include “primatized” antibodies comprising variable domain antigen-binding sequences derived from a non-human primate (e.g. Old World Monkey or Ape) and human constant region sequences.

An “intact antibody” herein is one comprising VL and VH domains, as well as a light chain constant domain (CL) and heavy chain constant domains, CH1, CH2 and CH3. The constant domains may be native sequence constant domains (e.g. human native sequence constant domains) or amino acid sequence variant thereof. The intact antibody may have one or more “effector functions” which refer to those biological activities attributable to the Fc region (a native sequence Fc region or amino acid sequence variant Fc region) of an antibody. Examples of antibody effector functions include C1q binding; complement dependent cytotoxicity; Fc receptor binding; antibody-dependent cell-mediated cytotoxicity (ADCC); phagocytosis; and down regulation of cell surface receptors such as B cell receptor and BCR.

Depending on the amino acid sequence of the constant domain of their heavy chains, intact antibodies can be assigned to different “classes.” There are five major classes of intact antibodies: IgA, IgD, IgE, IgG, and IgM, and several of these may be further divided into “subclasses” (isotypes), e.g., IgG1, IgG2, IgG3, IgG4, IgA, and IgA2. The heavy-chain constant domains that correspond to the different classes of antibodies are called α, δ, ε, γ, and μ, respectively. The subunit structures and three-dimensional configurations of different classes of immunoglobulins are well known.

Modification of Antibodies

The antibodies disclosed herein may be modified. For example, tomake them less immunogenic to a human subject. This may be achieved using any of a number of techniques familiar to the person skilled in the art. Some of these techniques are described in more detail below.

Humanisation

Techniques to reduce the in vivo immunogenicity of a non-human antibody or antibody fragment include those termed “humanisation”.

A “humanized antibody” refers to a polypeptide comprising at least a portion of a modified variable region of a human antibody wherein a portion of the variable region, preferably a portion substantially less than the intact human variable domain, has been substituted by the corresponding sequence from a non-human species and wherein the modified variable region is linked to at least another part of another protein, preferably the constant region of a human antibody. The expression “humanized antibodies” includes human antibodies in which one or more complementarity determining region (“CDR”) amino acid residues and/or one or more framework region (“FW” or “FR”) amino acid residues are substituted by amino acid residues from analogous sites in rodent or other non-human antibodies. The expression “humanized antibody” also includes an immunoglobulin amino acid sequence variant or fragment thereof that comprises an FR having substantially the amino acid sequence of a human immunoglobulin and a CDR having substantially the amino acid sequence of a non-human immunoglobulin.

“Humanized” forms of non-human (e.g., murine) antibodies are chimeric antibodies that contain minimal sequence derived from non-human immunoglobulin. Or, looked at another way, a humanized antibody is a human antibody that also contains selected sequences from non-human (e.g. murine) antibodies in place of the human sequences. A humanized antibody can include conservative amino acid substitutions or non-natural residues from the same or different species that do not significantly alter its binding and/or biologic activity. Such antibodies are chimeric antibodies that contain minimal sequence derived from non-human immunoglobulins.

There are a range of humanisation techniques, including ‘CDR grafting’, ‘guided selection’, ‘deimmunization’, ‘resurfacing’ (also known as ‘veneering’), ‘composite antibodies’, ‘Human String Content Optimisation’ and framework shuffling.

CDR Grafting

In this technique, the humanized antibodies are human immunoglobulins (recipient antibody) in which residues from a complementary-determining region (CDR) of the recipient antibody are replaced by residues from a CDR of a non-human species (donor antibody) such as mouse, rat, camel, bovine, goat, or rabbit having the desired properties (in effect, the non-human CDRs are ‘grafted’ onto the human framework). In some instances, framework region (FR) residues of the human immunoglobulin are replaced by corresponding non-human residues (this may happen when, for example, a particular FR residue has significant effect on antigen binding).

Furthermore, humanized antibodies can comprise residues that are found neither in the recipient antibody nor in the imported CDR or framework sequences. These modifications are made to further refine and maximize antibody performance. Thus, in general, a humanized antibody will comprise all of at least one, and in one aspect two, variable domains, in which all or all of the hypervariable loops correspond to those of a non-human immunoglobulin and all or substantially all of the FR regions are those of a human immunoglobulin sequence. The humanized antibody optionally also will comprise at least a portion of an immunoglobulin constant region (Fc), or that of a human immunoglobulin.

Guided Selection

The method consists of combining the V_(H) or V_(L) domain of a given non-human antibody specific for a particular epitope with a human V_(H) or V_(L) library and specific human V domains are selected against the antigen of interest. This selected human VH is then combined with a VL library to generate a completely human VH×VL combination. The method is described in Nature Biotechnology (N.Y.) 12, (1994) 899-903.

Composite Antibodies

In this method, two or more segments of amino acid sequence from a human antibody are combined within the final antibody molecule. They are constructed by combining multiple human VH and VL sequence segments in combinations which limit or avoid human T cell epitopes in the final composite antibody V regions. Where required, T cell epitopes are limited or avoided by, exchanging V region segments contributing to or encoding a T cell epitope with alternative segments which avoid T cell epitopes. This method is described in US 2008/0206239 A1.

Deimmunization

This method involves the removal of human (or other second species) T-cell epitopes from the V regions of the therapeutic antibody (or other molecule). The therapeutic antibodies V-region sequence is analysed for the presence of MHC class II-binding motifs by, for example, comparison with databases of MHC-binding motifs (such as the “motifs” database hosted at wehi.edu.au). Alternatively, MHC class II-binding motifs may be identified using computational threading methods such as those devised by Altuvia et al. (J. Mol. Biol. 249 244-250 (1995)); in these methods, consecutive overlapping peptides from the V-region sequences are testing for their binding energies to MHC class II proteins. This data can then be combined with information on other sequence features which relate to successfully presented peptides, such as amphipathicity, Rothbard motifs, and cleavage sites for cathepsin B and other processing enzymes.

Once potential second species (e.g. human) T-cell epitopes have been identified, they are eliminated by the alteration of one or more amino acids. The modified amino acids are usually within the T-cell epitope itself, but may also be adjacent to the epitope in terms of the primary or secondary structure of the protein (and therefore, may not be adjacent in the primary structure). Most typically, the alteration is by way of substitution but, in some circumstances amino acid addition or deletion will be more appropriate.

All alterations can be accomplished by recombinant DNA technology, so that the final molecule may be prepared by expression from a recombinant host using well established methods such as Site Directed Mutagenesis. However, the use of protein chemistry or any other means of molecular alteration is also possible.

Resurfacing

This method involves:

-   -   (a) determining the conformational structure of the variable         region of the non-human (e.g. rodent) antibody (or fragment         thereof) by constructing a three-dimensional model of the         non-human antibody variable region;     -   (b) generating sequence alignments using relative accessibility         distributions from x-ray crystallographic structures of a         sufficient number of non-human and human antibody variable         region heavy and light chains to give a set of heavy and light         chain framework positions wherein the alignment positions are         identical in 98% of the sufficient number of non-human antibody         heavy and light chains;     -   (c) defining for the non-human antibody to be humanized, a set         of heavy and light chain surface exposed amino acid residues         using the set of framework positions generated in step (b);     -   (d) identifying from human antibody amino acid sequences a set         of heavy and light chain surface exposed amino acid residues         that is most closely identical to the set of surface exposed         amino acid residues defined in step (c), wherein the heavy and         light chain from the human antibody are or are not naturally         paired;     -   (e) substituting, in the amino acid sequence of the non-human         antibody to be humanized, the set of heavy and light chain         surface exposed amino acid residues defined in step (c) with the         set of heavy and light chain surface exposed amino acid residues         identified in step (d);     -   (f) constructing a three-dimensional model of the variable         region of the non-human antibody resulting from the substituting         specified in step (e);     -   (g) identifying, by comparing the three-dimensional models         constructed in steps (a) and (f), any amino acid residues from         the sets identified in steps (c) or (d), that are within 5         Angstroms of any atom of any residue of the complementarity         determining regions of the non-human antibody to be humanized;         and     -   (h) changing any residues identified in step (g) from the human         to the original non-human amino acid residue to thereby define a         non-human antibody humanizing set of surface exposed amino acid         residues; with the proviso that step (a) need not be conducted         first, but must be conducted prior to step (g).         Superhumanization

The method compares the non-human sequence with the functional human germline gene repertoire. Those human genes encoding canonical structures identical or closely related to the non-human sequences are selected. Those selected human genes with highest homology within the CDRs are chosen as FR donors. Finally, the non-human CDRs are grafted onto these human FRs. This method is described in patent WO 2005/079479 A2.

Human String Content Optimization

This method compares the non-human (e.g. mouse) sequence with the repertoire of human germline genes and the differences are scored as Human String Content (HSC) that quantifies a sequence at the level of potential MHC/T-cell epitopes. The target sequence is then humanized by maximizing its HSC rather than using a global identity measure to generate multiple diverse humanized variants (described in Molecular Immunology, 44, (2007) 1986-1998).

Framework Shuffling

The CDRs of the non-human antibody are fused in-frame to cDNA pools encompassing all known heavy and light chain human germline gene frameworks. Humanised antibodies are then selected by e.g. panning of the phage displayed antibody library. This is described in Methods 36, 43-60 (2005).

Embodiments

Embodiments of the present invention include ConjA wherein the antibody is as defined above.

Embodiments of the present invention include ConjB wherein the antibody is as defined above.

Embodiments of the present invention include ConjC wherein the antibody is as defined above.

Drug Loading

The drug loading is the average number of PBD drugs per antibody, e.g. antibody. Where the compounds of the invention are bound to cysteines, drug loading may range from 1 to 8 drugs (D^(L)) per antibody, i.e. where 1, 2, 3, 4, 5, 6, 7, and 8 drug moieties are covalently attached to the antibody. Compositions of conjugates include collections of antibodies, conjugated with a range of drugs, from 1 to 8. Where the compounds of the invention are bound to lysines, drug loading may range from 1 to 80 drugs (D^(L)) per antibody, although an upper limit of 40, 20, 10 or 8 may be preferred. Compositions of conjugates include collections of antibodies, conjugated with a range of drugs, from 1 to 80, 1 to 40, 1 to 20, 1 to 10 or 1 to 8.

The average number of drugs per antibody in preparations of ADC from conjugation reactions may be characterized by conventional means such as UV, reverse phase HPLC, HIC, mass spectroscopy, ELISA assay, and electrophoresis. The quantitative distribution of ADC in terms of p may also be determined. By ELISA, the averaged value of p in a particular preparation of ADC may be determined (Hamblett et al (2004) Clin. Cancer Res. 10:7063-7070; Sanderson et al (2005) Clin. Cancer Res. 11:843-852). However, the distribution of p (drug) values is not discernible by the antibody-antigen binding and detection limitation of ELISA. Also, ELISA assay for detection of antibody-drug conjugates does not determine where the drug moieties are attached to the antibody, such as the heavy chain or light chain fragments, or the particular amino acid residues. In some instances, separation, purification, and characterization of homogeneous ADC where p is a certain value from ADC with other drug loadings may be achieved by means such as reverse phase HPLC or electrophoresis. Such techniques are also applicable to other types of conjugates.

For some antibody-drug conjugates, p may be limited by the number of attachment sites on the antibody. For example, an antibody may have only one or several cysteine thiol groups, or may have only one or several sufficiently reactive thiol groups through which a linker may be attached. Higher drug loading, e.g. p >5, may cause aggregation, insolubility, toxicity, or loss of cellular permeability of certain antibody-drug conjugates.

Typically, fewer than the theoretical maximum of drug moieties are conjugated to an antibody during a conjugation reaction. An antibody may contain, for example, many lysine residues that do not react with the drug-linker intermediate (D-L) or linker reagent. Only the most reactive lysine groups may react with an amine-reactive linker reagent. Also, only the most reactive cysteine thiol groups may react with a thiol-reactive linker reagent. Generally, antibodies do not contain many, if any, free and reactive cysteine thiol groups which may be linked to a drug moiety. Most cysteine thiol residues in the antibodies of the compounds exist as disulfide bridges and must be reduced with a reducing agent such as dithiothreitol (DTT) or TCEP, under partial or total reducing conditions. The loading (drug/antibody ratio) of an ADC may be controlled in several different manners, including: (i) limiting the molar excess of drug-linker intermediate (D-L) or linker reagent relative to antibody, (ii) limiting the conjugation reaction time or temperature, and (iii) partial or limiting reductive conditions for cysteine thiol modification.

Certain antibodies have reducible interchain disulfides, i.e. cysteine bridges. Antibodies may be made reactive for conjugation with linker reagents by treatment with a reducing agent such as DTT (dithiothreitol). Each cysteine bridge will thus form, theoretically, two reactive thiol nucleophiles. Additional nucleophilic groups can be introduced into antibodies through the reaction of lysines with 2-iminothiolane (Traut's reagent) resulting in conversion of an amine into a thiol. Reactive thiol groups may be introduced into the antibody (or fragment thereof) by engineering one, two, three, four, or more cysteine residues (e.g., preparing mutant antibodies comprising one or more non-native cysteine amino acid residues). U.S. Pat. No. 7,521,541 teaches engineering antibodies by introduction of reactive cysteine amino acids.

Cysteine amino acids may be engineered at reactive sites in an antibody and which do not form intrachain or intermolecular disulfide linkages (Junutula, et al., 2008b Nature Biotech., 26(8):925-932; Dornan et al (2009) Blood 114(13):2721-2729; U.S. Pat. No. 7,521,541; U.S. Pat. No. 7,723,485; WO2009/052249). The engineered cysteine thiols may react with linker reagents or the drug-linker reagents of the present invention which have thiol-reactive, electrophilic groups such as maleimide or alpha-halo amides to form ADC with cysteine engineered antibodies and the PBD drug moieties. The location of the drug moiety can thus be designed, controlled, and known. The drug loading can be controlled since the engineered cysteine thiol groups typically react with thiol-reactive linker reagents or drug-linker reagents in high yield. Engineering an IgG antibody to introduce a cysteine amino acid by substitution at a single site on the heavy or light chain gives two new cysteines on the symmetrical antibody. A drug loading near 2 can be achieved with near homogeneity of the conjugation product ADC.

Alternatively, site-specific conjugation can be achieved by engineering antibodies to contain unnatural amino acids in their heavy and/or light chains as described by Axup et al. ((2012), Proc Natl Acad Sci USA. 109(40):16101-16116). The unnatural amino acids provide the additional advantage that orthogonal chemistry can be designed to attach the linker reagent and drug.

Where more than one nucleophilic or electrophilic group of the antibody reacts with a drug-linker intermediate, or linker reagent followed by drug moiety reagent, then the resulting product is a mixture of ADC compounds with a distribution of drug moieties attached to an antibody, e.g. 1, 2, 3, etc. Liquid chromatography methods such as polymeric reverse phase (PLRP) and hydrophobic interaction (HIC) may separate compounds in the mixture by drug loading value. Preparations of ADC with a single drug loading value (p) may be isolated, however, these single loading value ADCs may still be heterogeneous mixtures because the drug moieties may be attached, via the linker, at different sites on the antibody.

Thus the antibody-drug conjugate compositions of the invention include mixtures of antibody-drug conjugate compounds where the antibody has one or more PBD drug moieties and where the drug moieties may be attached to the antibody at various amino acid residues.

In one embodiment, the average number of dimer pyrrolobenzodiazepine groups per antibody is in the range 1 to 20. In some embodiments the range is selected from 1 to 8, 2 to 8, 2 to 6, 2 to 4, and 4 to 8.

In some embodiments, there is one dimer pyrrolobenzodiazepine group per antibody.

Includes Other Forms

Unless otherwise specified, included in the above are the well known ionic, salt, solvate, and protected forms of these substituents. For example, a reference to carboxylic acid (—COOH) also includes the anionic (carboxylate) form (—COO⁻), a salt or solvate thereof, as well as conventional protected forms. Similarly, a reference to an amino group includes the protonated form (—N⁺HR¹R²), a salt or solvate of the amino group, for example, a hydrochloride salt, as well as conventional protected forms of an amino group. Similarly, a reference to a hydroxyl group also includes the anionic form (—O⁻), a salt or solvate thereof, as well as conventional protected forms.

Salts

It may be convenient or desirable to prepare, purify, and/or handle a corresponding salt of the active compound, for example, a pharmaceutically-acceptable salt. Examples of pharmaceutically acceptable salts are discussed in Berge, et al., J. Pharm. Sci., 66, 1-19 (1977).

For example, if the compound is anionic, or has a functional group which may be anionic (e.g. —COOH may be —COO⁻), then a salt may be formed with a suitable cation. Examples of suitable inorganic cations include, but are not limited to, alkali metal ions such as Na⁺ and K⁺, alkaline earth cations such as Ca²⁺ and Mg²⁺, and other cations such as Al⁺³. Examples of suitable organic cations include, but are not limited to, ammonium ion (i.e. NH₄ ⁺) and substituted ammonium ions (e.g. NH₃R⁺, NH₂R₂ ⁺, NHR₃ ⁺, NR₄ ⁺). Examples of some suitable substituted ammonium ions are those derived from: ethylamine, diethylamine, dicyclohexylamine, triethylamine, butylamine, ethylenediamine, ethanolamine, diethanolamine, piperazine, benzylamine, phenylbenzylamine, choline, meglumine, and tromethamine, as well as amino acids, such as lysine and arginine. An example of a common quaternary ammonium ion is N(CH₃)₄ ⁺.

If the compound is cationic, or has a functional group which may be cationic (e.g. —NH₂ may be —NH₃ ⁺), then a salt may be formed with a suitable anion. Examples of suitable inorganic anions include, but are not limited to, those derived from the following inorganic acids: hydrochloric, hydrobromic, hydroiodic, sulfuric, sulfurous, nitric, nitrous, phosphoric, and phosphorous.

Examples of suitable organic anions include, but are not limited to, those derived from the following organic acids: 2-acetyoxybenzoic, acetic, ascorbic, aspartic, benzoic, camphorsulfonic, cinnamic, citric, edetic, ethanedisulfonic, ethanesulfonic, fumaric, glucoheptonic, gluconic, glutamic, glycolic, hydroxymaleic, hydroxynaphthalene carboxylic, isethionic, lactic, lactobionic, lauric, maleic, malic, methanesulfonic, mucic, oleic, oxalic, palmitic, pamoic, pantothenic, phenylacetic, phenylsulfonic, propionic, pyruvic, salicylic, stearic, succinic, sulfanilic, tartaric, toluenesulfonic, trifluoroacetic acid and valeric. Examples of suitable polymeric organic anions include, but are not limited to, those derived from the following polymeric acids: tannic acid, carboxymethyl cellulose.

Solvates

It may be convenient or desirable to prepare, purify, and/or handle a corresponding solvate of the active compound. The term “solvate” is used herein in the conventional sense to refer to a complex of solute (e.g. active compound, salt of active compound) and solvent. If the solvent is water, the solvate may be conveniently referred to as a hydrate, for example, a mono-hydrate, a di-hydrate, a tri-hydrate, etc.

The invention includes compounds where a solvent adds across the imine bond of the PBD moiety, which is illustrated below where the solvent is water or an alcohol (R^(A)OH, where R^(A) is C₁₋₄ alkyl):

These forms can be called the carbinolamine and carbinolamine ether forms of the PBD (as described in the section relating to R¹⁰ above). The balance of these equilibria depend on the conditions in which the compounds are found, as well as the nature of the moiety itself.

These particular compounds may be isolated in solid form, for example, by lyophilisation.

Isomers

Certain compounds of the invention may exist in one or more particular geometric, optical, enantiomeric, diasteriomeric, epimeric, atropic, stereoisomeric, tautomeric, conformational, or anomeric forms, including but not limited to, cis- and trans-forms; E- and Z-forms; c-, t-, and r-forms; endo- and exo-forms; R-, S-, and meso-forms; D- and L-forms; d- and I-forms; (+) and (−) forms; keto-, enol-, and enolate-forms; syn- and anti-forms; synclinal- and anticlinal-forms; α- and β-forms; axial and equatorial forms; boat-, chair-, twist-, envelope-, and halfchair-forms; and combinations thereof, hereinafter collectively referred to as “isomers” (or “isomeric forms”).

The term “chiral” refers to molecules which have the property of non-superimposability of the mirror image partner, while the term “achiral” refers to molecules which are superimposable on their mirror image partner.

The term “stereoisomers” refers to compounds which have identical chemical constitution, but differ with regard to the arrangement of the atoms or groups in space.

“Diastereomer” refers to a stereoisomer with two or more centers of chirality and whose molecules are not mirror images of one another. Diastereomers have different physical properties, e.g. melting points, boiling points, spectral properties, and reactivities. Mixtures of diastereomers may separate under high resolution analytical procedures such as electrophoresis and chromatography.

“Enantiomers” refer to two stereoisomers of a compound which are non-superimposable mirror images of one another.

Stereochemical definitions and conventions used herein generally follow S. P. Parker, Ed., McGraw-Hill Dictionary of Chemical Terms (1984) McGraw-Hill Book Company, New York; and Eliel, E. and Wilen, S., “Stereochemistry of Organic Compounds”, John Wiley & Sons, Inc., New York, 1994. The compounds of the invention may contain asymmetric or chiral centers, and therefore exist in different stereoisomeric forms. It is intended that all stereoisomeric forms of the compounds of the invention, including but not limited to, diastereomers, enantiomers and atropisomers, as well as mixtures thereof such as racemic mixtures, form part of the present invention. Many organic compounds exist in optically active forms, i.e., they have the ability to rotate the plane of plane-polarized light. In describing an optically active compound, the prefixes D and L, or R and S, are used to denote the absolute configuration of the molecule about its chiral center(s). The prefixes d and l or (+) and (−) are employed to designate the sign of rotation of plane-polarized light by the compound, with (−) or l meaning that the compound is levorotatory. A compound prefixed with (+) or d is dextrorotatory. For a given chemical structure, these stereoisomers are identical except that they are mirror images of one another. A specific stereoisomer may also be referred to as an enantiomer, and a mixture of such isomers is often called an enantiomeric mixture. A 50:50 mixture of enantiomers is referred to as a racemic mixture or a racemate, which may occur where there has been no stereoselection or stereospecificity in a chemical reaction or process. The terms “racemic mixture” and “racemate” refer to an equimolar mixture of two enantiomeric species, devoid of optical activity.

Note that, except as discussed below for tautomeric forms, specifically excluded from the term “isomers”, as used herein, are structural (or constitutional) isomers (i.e. isomers which differ in the connections between atoms rather than merely by the position of atoms in space). For example, a reference to a methoxy group, —OCH₃, is not to be construed as a reference to its structural isomer, a hydroxymethyl group, —CH₂OH. Similarly, a reference to ortho-chlorophenyl is not to be construed as a reference to its structural isomer, meta-chlorophenyl. However, a reference to a class of structures may well include structurally isomeric forms falling within that class (e.g. C₁₋₇ alkyl includes n-propyl and iso-propyl; butyl includes n-, iso-, sec-, and tert-butyl; methoxyphenyl includes ortho-, meta-, and para-methoxyphenyl).

The above exclusion does not pertain to tautomeric forms, for example, keto-, enol-, and enolate-forms, as in, for example, the following tautomeric pairs: keto/enol (illustrated below), imine/enamine, amide/imino alcohol, amidine/amidine, nitroso/oxime, thioketone/enethiol, N-nitroso/hyroxyazo, and nitro/aci-nitro.

The term “tautomer” or “tautomeric form” refers to structural isomers of different energies which are interconvertible via a low energy barrier. For example, proton tautomers (also known as prototropic tautomers) include interconversions via migration of a proton, such as keto-enol and imine-enamine isomerizations. Valence tautomers include interconversions by reorganization of some of the bonding electrons.

Note that specifically included in the term “isomer” are compounds with one or more isotopic substitutions. For example, H may be in any isotopic form, including ¹H, ²H (D), and ³H (T); C may be in any isotopic form, including ¹²C ¹³C, and ¹⁴C; O may be in any isotopic form, including ¹⁶O and ¹⁸O; and the like.

Examples of isotopes that can be incorporated into compounds of the invention include isotopes of hydrogen, carbon, nitrogen, oxygen, phosphorous, fluorine, and chlorine, such as, but not limited to ²H (deuterium, D), ³H (tritium), ¹¹C, ¹³C, ¹⁴C, ¹⁵N, ¹⁸F, ³¹P, ³²P, ³⁵S, ³⁶Cl, and ¹²⁵I. Various isotopically labeled compounds of the present invention, for example those into which radioactive isotopes such as 3H, 13C, and 14C are incorporated. Such isotopically labelled compounds may be useful in metabolic studies, reaction kinetic studies, detection or imaging techniques, such as positron emission tomography (PET) or single-photon emission computed tomography (SPECT) including drug or substrate tissue distribution assays, or in radioactive treatment of patients. Deuterium labelled or substituted therapeutic compounds of the invention may have improved DMPK (drug metabolism and pharmacokinetics) properties, relating to distribution, metabolism, and excretion (ADME). Substitution with heavier isotopes such as deuterium may afford certain therapeutic advantages resulting from greater metabolic stability, for example increased in vivo half-life or reduced dosage requirements. An 18F labeled compound may be useful for PET or SPECT studies. Isotopically labeled compounds of this invention and prodrugs thereof can generally be prepared by carrying out the procedures disclosed in the schemes or in the examples and preparations described below by substituting a readily available isotopically labeled reagent for a non-isotopically labeled reagent. Further, substitution with heavier isotopes, particularly deuterium (i.e., 2H or D) may afford certain therapeutic advantages resulting from greater metabolic stability, for example increased in vivo half-life or reduced dosage requirements or an improvement in therapeutic index. It is understood that deuterium in this context is regarded as a substituent. The concentration of such a heavier isotope, specifically deuterium, may be defined by an isotopic enrichment factor. In the compounds of this invention any atom not specifically designated as a particular isotope is meant to represent any stable isotope of that atom.

Unless otherwise specified, a reference to a particular compound includes all such isomeric forms, including (wholly or partially) racemic and other mixtures thereof. Methods for the preparation (e.g. asymmetric synthesis) and separation (e.g. fractional crystallisation and chromatographic means) of such isomeric forms are either known in the art or are readily obtained by adapting the methods taught herein, or known methods, in a known manner.

Biological Activity

In Vitro Cell Proliferation Assays

Generally, the cytotoxic or cytostatic activity of an antibody-drug conjugate (ADC) is measured by: exposing mammalian cells having receptor proteins to the antibody of the ADC in a cell culture medium; culturing the cells for a period from about 6 hours to about 5 days; and measuring cell viability. Cell-based in vitro assays are used to measure viability (proliferation), cytotoxicity, and induction of apoptosis (caspase activation) of an ADC of the invention.

The in vitro potency of antibody-drug conjugates can be measured by a cell proliferation assay. The CellTiter-Glo® Luminescent Cell Viability Assay is a commercially available (Promega Corp., Madison, Wis.), homogeneous assay method based on the recombinant expression of Coleoptera luciferase (U.S. Pat. Nos. 5,583,024; 5,674,713 and 5,700,670). This cell proliferation assay determines the number of viable cells in culture based on quantitation of the ATP present, an indicator of metabolically active cells (Crouch et al (1993) J. Immunol. Meth. 160:81-88; U.S. Pat. No. 6,602,677). The CeIlTiter-Glo® Assay is conducted in 96 well format, making it amenable to automated high-throughput screening (HTS) (Cree et al (1995) AntiCancer Drugs 6:398-404). The homogeneous assay procedure involves adding the single reagent (CeIlTiter-Glo® Reagent) directly to cells cultured in serum-supplemented medium. Cell washing, removal of medium and multiple pipetting steps are not required. The system detects as few as 15 cells/well in a 384-well format in 10 minutes after adding reagent and mixing. The cells may be treated continuously with ADC, or they may be treated and separated from ADC. Generally, cells treated briefly, i.e. 3 hours, showed the same potency effects as continuously treated cells.

The homogeneous “add-mix-measure” format results in cell lysis and generation of a luminescent signal proportional to the amount of ATP present. The amount of ATP is directly proportional to the number of cells present in culture. The CeIlTiter-Glo® Assay generates a “glow-type” luminescent signal, produced by the luciferase reaction, which has a half-life generally greater than five hours, depending on cell type and medium used. Viable cells are reflected in relative luminescence units (RLU). The substrate, Beetle Luciferin, is oxidatively decarboxylated by recombinant firefly luciferase with concomitant conversion of ATP to AMP and generation of photons.

The in vitro potency of antibody-drug conjugates can also be measured by a cytotoxicity assay. Cultured adherent cells are washed with PBS, detached with trypsin, diluted in complete medium, containing 10% FCS, centrifuged, re-suspended in fresh medium and counted with a haemocytometer. Suspension cultures are counted directly. Monodisperse cell suspensions suitable for counting may require agitation of the suspension by repeated aspiration to break up cell clumps.

The cell suspension is diluted to the desired seeding density and dispensed (100 μl per well) into black 96 well plates. Plates of adherent cell lines are incubated overnight to allow adherence. Suspension cell cultures can be used on the day of seeding.

A stock solution (1 ml) of ADC (20 μg/ml) is made in the appropriate cell culture medium. Serial 10-fold dilutions of stock ADC are made in 15 ml centrifuge tubes by serially transferring 100 μl to 900 μl of cell culture medium.

Four replicate wells of each ADC dilution (100 μl) are dispensed in 96-well black plates, previously plated with cell suspension (100 μl), resulting in a final volume of 200 μl. Control wells receive cell culture medium (100 μl).

If the doubling time of the cell line is greater than 30 hours, ADC incubation is for 5 days, otherwise a four day incubation is done.

At the end of the incubation period, cell viability is assessed with the Alamar blue assay. AlamarBlue (Invitrogen) is dispensed over the whole plate (20 μl per well) and incubated for 4 hours. Alamar blue fluorescence is measured at excitation 570 nm, emission 585 nm on the Varioskan flash plate reader. Percentage cell survival is calculated from the mean fluorescence in the ADC treated wells compared to the mean fluorescence in the control wells.

Use

The conjugates of the invention may be used to provide a PBD compound at a target location.

The target location is preferably a proliferative cell population. The antibody is an antibody for an antigen present on a proliferative cell population.

In one embodiment the antigen is absent or present at a reduced level in a non-proliferative cell population compared to the amount of antigen present in the proliferative cell population, for example a tumour cell population.

At the target location the linker may be cleaved so as to release a compound RelA, RelB, or RelC. Thus, the conjugate may be used to selectively provide a compound RelA, RelB or RelC to the target location.

The linker may be cleaved by an enzyme present at the target location.

The target location may be in vitro, in vivo or ex vivo.

The antibody-drug conjugate (ADC) compounds of the invention include those with utility for anticancer activity. In particular, the compounds include an antibody conjugated, i.e. covalently attached by a linker, to a PBD drug moiety, i.e. toxin. When the drug is not conjugated to an antibody, the PBD drug has a cytotoxic effect. The biological activity of the PBD drug moiety is thus modulated by conjugation to an antibody. The antibody-drug conjugates (ADC) of the invention selectively deliver an effective dose of a cytotoxic agent to tumor tissue whereby greater selectivity, i.e. a lower efficacious dose, may be achieved.

Thus, in one aspect, the present invention provides a conjugate compound as described herein for use in therapy.

In a further aspect there is also provides a conjugate compound as described herein for use in the treatment of a proliferative disease. A second aspect of the present invention provides the use of a conjugate compound in the manufacture of a medicament for treating a proliferative disease.

One of ordinary skill in the art is readily able to determine whether or not a candidate conjugate treats a proliferative condition for any particular cell type. For example, assays which may conveniently be used to assess the activity offered by a particular compound are described in the examples below.

The term “proliferative disease” pertains to an unwanted or uncontrolled cellular proliferation of excessive or abnormal cells which is undesired, such as, neoplastic or hyperplastic growth, whether in vitro or in vivo.

Examples of proliferative conditions include, but are not limited to, benign, pre-malignant, and malignant cellular proliferation, including but not limited to, neoplasms and tumours (e.g. histocytoma, glioma, astrocyoma, osteoma), cancers (e.g. lung cancer, small cell lung cancer, gastrointestinal cancer, bowel cancer, colon cancer, breast carinoma, ovarian carcinoma, prostate cancer, testicular cancer, liver cancer, kidney cancer, bladder cancer, pancreas cancer, brain cancer, sarcoma, osteosarcoma, Kaposi's sarcoma, melanoma), lymphomas, leukemias, psoriasis, bone diseases, fibroproliferative disorders (e.g. of connective tissues), and atherosclerosis. Cancers of particular interest include, but are not limited to, leukemias and ovarian cancers.

Any type of cell may be treated, including but not limited to, lung, gastrointestinal (including, e.g. bowel, colon), breast (mammary), ovarian, prostate, liver (hepatic), kidney (renal), bladder, pancreas, brain, and skin.

Cancers of particular interest include, but are not limited to, prostate cancers.

PSMA has also shown to be widely expressed in the neovasculature of non-prostate solid tumors including carcinomas of the colon, breast, bladder, pancreas, kidney and melanoma, but not normal vasculature. Thus, a PSMA specific ADC can be used for the treatment of non-prostate tumors with PSMA positive neovasculature.

It is contemplated that the antibody-drug conjugates (ADC) of the present invention may be used to treat various diseases or disorders, e.g. characterized by the overexpression of a tumor antigen. Exemplary conditions or hyperproliferative disorders include benign or malignant tumors; leukemia, haematological, and lymphoid malignancies. Others include neuronal, glial, astrocytal, hypothalamic, glandular, macrophagal, epithelial, stromal, blastocoelic, inflammatory, angiogenic and immunologic, including autoimmune, disorders.

Generally, the disease or disorder to be treated is a hyperproliferative disease such as cancer. Examples of cancer to be treated herein include, but are not limited to, carcinoma, lymphoma, blastoma, sarcoma, and leukemia or lymphoid malignancies. More particular examples of such cancers include squamous cell cancer (e.g. epithelial squamous cell cancer), lung cancer including small-cell lung cancer, non-small cell lung cancer, adenocarcinoma of the lung and squamous carcinoma of the lung, cancer of the peritoneum, hepatocellular cancer, gastric or stomach cancer including gastrointestinal cancer, pancreatic cancer, glioblastoma, cervical cancer, ovarian cancer, liver cancer, bladder cancer, hepatoma, breast cancer, colon cancer, rectal cancer, colorectal cancer, endometrial or uterine carcinoma, salivary gland carcinoma, kidney or renal cancer, prostate cancer, vulval cancer, thyroid cancer, hepatic carcinoma, anal carcinoma, penile carcinoma, as well as head and neck cancer.

Autoimmune diseases for which the ADC compounds may be used in treatment include rheumatologic disorders (such as, for example, rheumatoid arthritis, Sjögren's syndrome, scleroderma, lupus such as SLE and lupus nephritis, polymyositis/dermatomyositis, cryoglobulinemia, anti-phospholipid antibody syndrome, and psoriatic arthritis), osteoarthritis, autoimmune gastrointestinal and liver disorders (such as, for example, inflammatory bowel diseases (e.g. ulcerative colitis and Crohn's disease), autoimmune gastritis and pernicious anemia, autoimmune hepatitis, primary biliary cirrhosis, primary sclerosing cholangitis, and celiac disease), vasculitis (such as, for example, ANCA-associated vasculitis, including Churg-Strauss vasculitis, Wegener's granulomatosis, and polyarteriitis), autoimmune neurological disorders (such as, for example, multiple sclerosis, opsoclonus myoclonus syndrome, myasthenia gravis, neuromyelitis optica, Parkinson's disease, Alzheimer's disease, and autoimmune polyneuropathies), renal disorders (such as, for example, glomerulonephritis, Goodpasture's syndrome, and Berger's disease), autoimmune dermatologic disorders (such as, for example, psoriasis, urticaria, hives, pemphigus vulgaris, bullous pemphigoid, and cutaneous lupus erythematosus), hematologic disorders (such as, for example, thrombocytopenic purpura, thrombotic thrombocytopenic purpura, post-transfusion purpura, and autoimmune hemolytic anemia), atherosclerosis, uveitis, autoimmune hearing diseases (such as, for example, inner ear disease and hearing loss), Behcet's disease, Raynaud's syndrome, organ transplant, and autoimmune endocrine disorders (such as, for example, diabetic-related autoimmune diseases such as insulin-dependent diabetes mellitus (IDDM), Addison's disease, and autoimmune thyroid disease (e.g. Graves' disease and thyroiditis)). More preferred such diseases include, for example, rheumatoid arthritis, ulcerative colitis, ANCA-associated vasculitis, lupus, multiple sclerosis, Sjögren's syndrome, Graves' disease, IDDM, pernicious anemia, thyroiditis, and glomerulonephritis.

Methods of Treatment

The conjugates of the present invention may be used in a method of therapy. Also provided is a method of treatment, comprising administering to a subject in need of treatment a therapeutically-effective amount of a conjugate compound of the invention. The term “therapeutically effective amount” is an amount sufficient to show benefit to a patient. Such benefit may be at least amelioration of at least one symptom. The actual amount administered, and rate and time-course of administration, will depend on the nature and severity of what is being treated. Prescription of treatment, e.g. decisions on dosage, is within the responsibility of general practitioners and other medical doctors.

A compound of the invention may be administered alone or in combination with other treatments, either simultaneously or sequentially dependent upon the condition to be treated. Examples of treatments and therapies include, but are not limited to, chemotherapy (the administration of active agents, including, e.g. drugs, such as chemotherapeutics); surgery; and radiation therapy.

A “chemotherapeutic agent” is a chemical compound useful in the treatment of cancer, regardless of mechanism of action. Classes of chemotherapeutic agents include, but are not limited to: alkylating agents, antimetabolites, spindle poison plant alkaloids, cytotoxic/antitumor antibiotics, topoisomerase inhibitors, antibodies, photosensitizers, and kinase inhibitors. Chemotherapeutic agents include compounds used in “targeted therapy” and conventional chemotherapy.

Examples of chemotherapeutic agents include: erlotinib (TARCEVA®, Genentech/OSI Pharm.), docetaxel (TAXOTERE®, Sanofi-Aventis), 5-FU (fluorouracil, 5-fluorouracil, CAS No. 51-21-8), gemcitabine (GEMZAR®, Lilly), PD-0325901 (CAS No. 391210-10-9, Pfizer), cisplatin (cis-diamine, dichloroplatinum(II), CAS No. 15663-27-1), carboplatin (CAS No. 41575-94-4), paclitaxel (TAXOL®, Bristol-Myers Squibb Oncology, Princeton, N.J.), trastuzumab (HERCEPTIN®, Genentech), temozolomide (4-methyl-5-oxo-2,3,4,6,8-pentazabicyclo [4.3.0] nona-2,7,9-triene-9-carboxamide, CAS No. 85622-93-1, TEMODAR®, TEMODAL®, Schering Plough), tamoxifen ((Z)-2-[4-(1,2-diphenylbut-1-enyl)phenoxy]-N,N-dimethylethanamine, NOLVADEX®, ISTUBAL®, VALODEX®), and doxorubicin (ADRIAMYCIN®), Akti-1/2, HPPD, and rapamycin.

More examples of chemotherapeutic agents include: oxaliplatin (ELOXATIN®, Sanofi), bortezomib (VELCADE®, Millennium Pharm.), sutent (SUNITINIB®, SU11248, Pfizer), letrozole (FEMARA®, Novartis), imatinib mesylate (GLEEVEC®, Novartis), XL-518 (Mek inhibitor, Exelixis, WO 2007/044515), ARRY-886 (Mek inhibitor, AZD6244, Array BioPharma, Astra Zeneca), SF-1126 (PI3K inhibitor, Semafore Pharmaceuticals), BEZ-235 (PI3K inhibitor, Novartis), XL-147 (PI3K inhibitor, Exelixis), PTK787/ZK 222584 (Novartis), fulvestrant (FASLODEX®, AstraZeneca), leucovorin (folinic acid), rapamycin (sirolimus, RAPAMUNE®, Wyeth), lapatinib (TYKERB®, GSK572016, Glaxo Smith Kline), lonafarnib (SARASAR™, SCH 66336, Schering Plough), sorafenib (NEXAVAR®, BAY43-9006, Bayer Labs), gefitinib (IRESSA®, AstraZeneca), irinotecan (CAMPTOSAR®, CPT-11, Pfizer), tipifarnib (ZARNESTRA™, Johnson & Johnson), ABRAXANE™ (Cremophor-free), albumin-engineered nanoparticle formulations of paclitaxel (American Pharmaceutical Partners, Schaumberg, II), vandetanib (rINN, ZD6474, ZACTIMA®, AstraZeneca), chloranmbucil, AG1478, AG1571 (SU 5271; Sugen), temsirolimus (TORISEL®, Wyeth), pazopanib (GlaxoSmithKline), canfosfamide (TELCYTA®, Telik), thiotepa and cyclosphosphamide (CYTOXAN®, NEOSAR®); alkyl sulfonates such as busulfan, improsulfan and piposulfan; aziridines such as benzodopa, carboquone, meturedopa, and uredopa; ethylenimines and methylamelamines including altretamine, triethylenemelamine, triethylenephosphoramide, triethylenethiophosphoramide and trimethylomelamine; acetogenins (especially bullatacin and bullatacinone); a camptothecin (including the synthetic analog topotecan); bryostatin; callystatin; CC-1065 (including its adozelesin, carzelesin and bizelesin synthetic analogs); cryptophycins (particularly cryptophycin 1 and cryptophycin 8); dolastatin; duocarmycin (including the synthetic analogs, KW-2189 and CBI-TM1); eleutherobin; pancratistatin; a sarcodictyin; spongistatin; nitrogen mustards such as chlorambucil, chlornaphazine, chlorophosphamide, estramustine, ifosfamide, mechlorethamine, mechlorethamine oxide hydrochloride, melphalan, novembichin, phenesterine, prednimustine, trofosfamide, uracil mustard; nitrosoureas such as carmustine, chlorozotocin, fotemustine, lomustine, nimustine, and ranimnustine; antibiotics such as the enediyne antibiotics (e.g. calicheamicin, calicheamicin gamma1I, calicheamicin omegal1 (Angew Chem. Intl. Ed. Engl. (1994) 33:183-186); dynemicin, dynemicin A; bisphosphonates, such as clodronate; an esperamicin; as well as neocarzinostatin chromophore and related chromoprotein enediyne antibiotic chromophores), aclacinomysins, actinomycin, authramycin, azaserine, bleomycins, cactinomycin, carabicin, carminomycin, carzinophilin, chromomycinis, dactinomycin, daunorubicin, detorubicin, 6-diazo-5-oxo-L-norleucine, morpholino-doxorubicin, cyanomorpholino-doxorubicin, 2-pyrrolino-doxorubicin and deoxydoxorubicin), epirubicin, esorubicin, idarubicin, nemorubicin, marcellomycin, mitomycins such as mitomycin C, mycophenolic acid, nogalamycin, olivomycins, peplomycin, porfiromycin, puromycin, quelamycin, rodorubicin, streptonigrin, streptozocin, tubercidin, ubenimex, zinostatin, zorubicin; anti-metabolites such as methotrexate and 5-fluorouracil (5-FU); folic acid analogs such as denopterin, methotrexate, pteropterin, trimetrexate; purine analogs such as fludarabine, 6-mercaptopurine, thiamiprine, thioguanine; pyrimidine analogs such as ancitabine, azacitidine, 6-azauridine, carmofur, cytarabine, dideoxyuridine, doxifluridine, enocitabine, floxuridine; androgens such as calusterone, dromostanolone propionate, epitiostanol, mepitiostane, testolactone; anti-adrenals such as aminoglutethimide, mitotane, trilostane; folic acid replenisher such as frolinic acid; aceglatone; aldophosphamide glycoside; aminolevulinic acid; eniluracil; amsacrine; bestrabucil; bisantrene; edatraxate; defofamine; demecolcine; diaziquone; elfornithine; elliptinium acetate; an epothilone; etoglucid; gallium nitrate; hydroxyurea; lentinan; lonidainine; maytansinoids such as maytansine and ansamitocins; mitoguazone; mitoxantrone; mopidanmol; nitraerine; pentostatin; phenamet; pirarubicin; losoxantrone; podophyllinic acid; 2-ethylhydrazide; procarbazine; PSK® polysaccharide complex (JHS Natural Products, Eugene, Oreg.); razoxane; rhizoxin; sizofiran; spirogermanium; tenuazonic acid; triaziquone; 2,2′,2″-trichlorotriethylamine; trichothecenes (especially T-2 toxin, verracurin A, roridin A and anguidine); urethan; vindesine; dacarbazine; mannomustine; mitobronitol; mitolactol; pipobroman; gacytosine; arabinoside (“Ara-C”); cyclophosphamide; thiotepa; 6-thioguanine; mercaptopurine; methotrexate; platinum analogs such as cisplatin and carboplatin; vinblastine; etoposide (VP-16); ifosfamide; mitoxantrone; vincristine; vinorelbine (NAVELBINE®); novantrone; teniposide; edatrexate; daunomycin; aminopterin; capecitabine (XELODA®, Roche); ibandronate; CPT-11; topoisomerase inhibitor RFS 2000; difluoromethylornithine (DMFO); retinoids such as retinoic acid; and pharmaceutically acceptable salts, acids and derivatives of any of the above.

Also included in the definition of “chemotherapeutic agent” are: (i) anti-hormonal agents that act to regulate or inhibit hormone action on tumors such as anti-estrogens and selective estrogen receptor modulators (SERMs), including, for example, tamoxifen (including NOLVADEX®; tamoxifen citrate), raloxifene, droloxifene, 4-hydroxytamoxifen, trioxifene, keoxifene, LY117018, onapristone, and FARESTON® (toremifine citrate); (ii) aromatase inhibitors that inhibit the enzyme aromatase, which regulates estrogen production in the adrenal glands, such as, for example, 4(5)-imidazoles, aminoglutethimide, MEGASE® (megestrol acetate), AROMASIN® (exemestane; Pfizer), formestanie, fadrozole, RIVISOR® (vorozole), FEMARA® (letrozole; Novartis), and ARIMIDEX® (anastrozole; AstraZeneca); (iii) anti-androgens such as flutamide, nilutamide, bicalutamide, leuprolide, and goserelin; as well as troxacitabine (a 1,3-dioxolane nucleoside cytosine analog); (iv) protein kinase inhibitors such as MEK inhibitors (WO 2007/044515); (v) lipid kinase inhibitors; (vi) antisense oligonucleotides, particularly those which inhibit expression of genes in signaling pathways implicated in aberrant cell proliferation, for example, PKC-alpha, Raf and H-Ras, such as oblimersen (GENASENSE®, Genta Inc.); (vii) ribozymes such as VEGF expression inhibitors (e.g., ANGIOZYME®) and HER2 expression inhibitors; (viii) vaccines such as gene therapy vaccines, for example, ALLOVECTIN®, LEUVECTIN®, and VAXID®; PROLEUKIN® rIL-2; topoisomerase 1 inhibitors such as LURTOTECAN®; ABARELIX® rmRH; (ix) anti-angiogenic agents such as bevacizumab (AVASTIN®, Genentech); and pharmaceutically acceptable salts, acids and derivatives of any of the above.

Also included in the definition of “chemotherapeutic agent” are therapeutic antibodies such as alemtuzumab (Campath), bevacizumab (AVASTIN®, Genentech); cetuximab (ERBITUX®, Imclone); panitumumab (VECTIBIX®, Amgen), rituximab (RITUXAN®, Genentech/Biogen Idec), ofatumumab (ARZERRA®, GSK), pertuzumab (PERJETA™, OMNITARG™, 2C4, Genentech), trastuzumab (HERCEPTIN®, Genentech), tositumomab (Bexxar, Corixia), and the antibody drug conjugate, gemtuzumab ozogamicin (MYLOTARG®, Wyeth).

Humanized monoclonal antibodies with therapeutic potential as chemotherapeutic agents in combination with the conjugates of the invention include: alemtuzumab, apolizumab, aselizumab, atlizumab, bapineuzumab, bevacizumab, bivatuzumab mertansine, cantuzumab mertansine, cedelizumab, certolizumab pegol, cidfusituzumab, cidtuzumab, daclizumab, eculizumab, efalizumab, epratuzumab, erlizumab, felvizumab, fontolizumab, gemtuzumab ozogamicin, inotuzumab ozogamicin, ipilimumab, labetuzumab, lintuzumab, matuzumab, mepolizumab, motavizumab, motovizumab, natalizumab, nimotuzumab, nolovizumab, numavizumab, ocrelizumab, omalizumab, palivizumab, pascolizumab, pecfusituzumab, pectuzumab, pertuzumab, pexelizumab, ralivizumab, ranibizumab, reslivizumab, reslizumab, resyvizumab, rovelizumab, ruplizumab, sibrotuzumab, siplizumab, sontuzumab, tacatuzumab tetraxetan, tadocizumab, talizumab, tefibazumab, tocilizumab, toralizumab, trastuzumab, tucotuzumab celmoleukin, tucusituzumab, umavizumab, urtoxazumab, and visilizumab.

Pharmaceutical compositions according to the present invention, and for use in accordance with the present invention, may comprise, in addition to the active ingredient, i.e. a conjugate compound, a pharmaceutically acceptable excipient, carrier, buffer, stabiliser or other materials well known to those skilled in the art. Such materials should be non-toxic and should not interfere with the efficacy of the active ingredient. The precise nature of the carrier or other material will depend on the route of administration, which may be oral, or by injection, e.g. cutaneous, subcutaneous, or intravenous.

Pharmaceutical compositions for oral administration may be in tablet, capsule, powder or liquid form. A tablet may comprise a solid carrier or an adjuvant. Liquid pharmaceutical compositions generally comprise a liquid carrier such as water, petroleum, animal or vegetable oils, mineral oil or synthetic oil. Physiological saline solution, dextrose or other saccharide solution or glycols such as ethylene glycol, propylene glycol or polyethylene glycol may be included. A capsule may comprise a solid carrier such a gelatin.

For intravenous, cutaneous or subcutaneous injection, or injection at the site of affliction, the active ingredient will be in the form of a parenterally acceptable aqueous solution which is pyrogen-free and has suitable pH, isotonicity and stability. Those of relevant skill in the art are well able to prepare suitable solutions using, for example, isotonic vehicles such as Sodium Chloride Injection, Ringer's Injection, Lactated Ringer's Injection. Preservatives, stabilisers, buffers, antioxidants and/or other additives may be included, as required.

Formulations

While it is possible for the conjugate compound to be used (e.g., administered) alone, it is often preferable to present it as a composition or formulation.

In one embodiment, the composition is a pharmaceutical composition (e.g., formulation, preparation, medicament) comprising a conjugate compound, as described herein, and a pharmaceutically acceptable carrier, diluent, or excipient.

In one embodiment, the composition is a pharmaceutical composition comprising at least one conjugate compound, as described herein, together with one or more other pharmaceutically acceptable ingredients well known to those skilled in the art, including, but not limited to, pharmaceutically acceptable carriers, diluents, excipients, adjuvants, fillers, buffers, preservatives, anti-oxidants, lubricants, stabilisers, solubilisers, surfactants (e.g., wetting agents), masking agents, colouring agents, flavouring agents, and sweetening agents.

In one embodiment, the composition further comprises other active agents, for example, other therapeutic or prophylactic agents.

Suitable carriers, diluents, excipients, etc. can be found in standard pharmaceutical texts. See, for example, Handbook of Pharmaceutical Additives, 2nd Edition (eds. M. Ash and I. Ash), 2001 (Synapse Information Resources, Inc., Endicott, N.Y., USA), Remington's Pharmaceutical Sciences, 20th edition, pub. Lippincott, Williams & Wilkins, 2000; and Handbook of Pharmaceutical Excipients, 2nd edition, 1994.

Another aspect of the present invention pertains to methods of making a pharmaceutical composition comprising admixing at least one [¹¹C]-radiolabelled conjugate or conjugate-like compound, as defined herein, together with one or more other pharmaceutically acceptable ingredients well known to those skilled in the art, e.g., carriers, diluents, excipients, etc. If formulated as discrete units (e.g., tablets, etc.), each unit contains a predetermined amount (dosage) of the active compound.

The term “pharmaceutically acceptable,” as used herein, pertains to compounds, ingredients, materials, compositions, dosage forms, etc., which are, within the scope of sound medical judgment, suitable for use in contact with the tissues of the subject in question (e.g., human) without excessive toxicity, irritation, allergic response, or other problem or complication, commensurate with a reasonable benefit/risk ratio. Each carrier, diluent, excipient, etc. must also be “acceptable” in the sense of being compatible with the other ingredients of the formulation.

The formulations may be prepared by any methods well known in the art of pharmacy. Such methods include the step of bringing into association the active compound with a carrier which constitutes one or more accessory ingredients. In general, the formulations are prepared by uniformly and intimately bringing into association the active compound with carriers (e.g., liquid carriers, finely divided solid carrier, etc.), and then shaping the product, if necessary.

The formulation may be prepared to provide for rapid or slow release; immediate, delayed, timed, or sustained release; or a combination thereof.

Formulations suitable for parenteral administration (e.g., by injection), include aqueous or non-aqueous, isotonic, pyrogen-free, sterile liquids (e.g., solutions, suspensions), in which the active ingredient is dissolved, suspended, or otherwise provided (e.g., in a liposome or other microparticulate). Such liquids may additional contain other pharmaceutically acceptable ingredients, such as anti-oxidants, buffers, preservatives, stabilisers, bacteriostats, suspending agents, thickening agents, and solutes which render the formulation isotonic with the blood (or other relevant bodily fluid) of the intended recipient. Examples of excipients include, for example, water, alcohols, polyols, glycerol, vegetable oils, and the like. Examples of suitable isotonic carriers for use in such formulations include Sodium Chloride Injection, Ringer's Solution, or Lactated Ringer's Injection. Typically, the concentration of the active ingredient in the liquid is from about 1 ng/ml to about 10 μg/ml, for example from about 10 ng/ml to about 1 μg/ml. The formulations may be presented in unit-dose or multi-dose sealed containers, for example, ampoules and vials, and may be stored in a freeze-dried (lyophilised) condition requiring only the addition of the sterile liquid carrier, for example water for injections, immediately prior to use. Extemporaneous injection solutions and suspensions may be prepared from sterile powders, granules, and tablets.

Dosage

It will be appreciated by one of skill in the art that appropriate dosages of the conjugate compound, and compositions comprising the conjugate compound, can vary from patient to patient. Determining the optimal dosage will generally involve the balancing of the level of therapeutic benefit against any risk or deleterious side effects. The selected dosage level will depend on a variety of factors including, but not limited to, the activity of the particular compound, the route of administration, the time of administration, the rate of excretion of the compound, the duration of the treatment, other drugs, compounds, and/or materials used in combination, the severity of the condition, and the species, sex, age, weight, condition, general health, and prior medical history of the patient. The amount of compound and route of administration will ultimately be at the discretion of the physician, veterinarian, or clinician, although generally the dosage will be selected to achieve local concentrations at the site of action which achieve the desired effect without causing substantial harmful or deleterious side-effects.

Administration can be effected in one dose, continuously or intermittently (e.g., in divided doses at appropriate intervals) throughout the course of treatment. Methods of determining the most effective means and dosage of administration are well known to those of skill in the art and will vary with the formulation used for therapy, the purpose of the therapy, the target cell(s) being treated, and the subject being treated. Single or multiple administrations can be carried out with the dose level and pattern being selected by the treating physician, veterinarian, or clinician.

In general, a suitable dose of the active compound is in the range of about 100 ng to about 25 mg (more typically about 1 μg to about 10 mg) per kilogram body weight of the subject per day. Where the active compound is a salt, an ester, an amide, a prodrug, or the like, the amount administered is calculated on the basis of the parent compound and so the actual weight to be used is increased proportionately.

In one embodiment, the active compound is administered to a human patient according to the following dosage regime: about 100 mg, 3 times daily.

In one embodiment, the active compound is administered to a human patient according to the following dosage regime: about 150 mg, 2 times daily.

In one embodiment, the active compound is administered to a human patient according to the following dosage regime: about 200 mg, 2 times daily.

However in one embodiment, the conjugate compound is administered to a human patient according to the following dosage regime: about 50 or about 75 mg, 3 or 4 times daily.

In one embodiment, the conjugate compound is administered to a human patient according to the following dosage regime: about 100 or about 125 mg, 2 times daily.

The dosage amounts described above may apply to the conjugate (including the PBD moiety and the linker to the antibody) or to the effective amount of PBD compound provided, for example the amount of compound that is releasable after cleavage of the linker.

For the prevention or treatment of disease, the appropriate dosage of an ADC of the invention will depend on the type of disease to be treated, as defined above, the severity and course of the disease, whether the molecule is administered for preventive or therapeutic purposes, previous therapy, the patient's clinical history and response to the antibody, and the discretion of the attending physician. The molecule is suitably administered to the patient at one time or over a series of treatments. Depending on the type and severity of the disease, about 1 μg/kg to 15 mg/kg (e.g. 0.1-20 mg/kg) of molecule is an initial candidate dosage for administration to the patient, whether, for example, by one or more separate administrations, or by continuous infusion. A typical daily dosage might range from about 1 μg/kg to 100 mg/kg or more, depending on the factors mentioned above. An exemplary dosage of ADC to be administered to a patient is in the range of about 0.1 to about 10 mg/kg of patient weight. For repeated administrations over several days or longer, depending on the condition, the treatment is sustained until a desired suppression of disease symptoms occurs. An exemplary dosing regimen comprises a course of administering an initial loading dose of about 4 mg/kg, followed by additional doses every week, two weeks, or three weeks of an ADC. Other dosage regimens may be useful. The progress of this therapy is easily monitored by conventional techniques and assays.

Treatment

The term “treatment,” as used herein in the context of treating a condition, pertains generally to treatment and therapy, whether of a human or an animal (e.g., in veterinary applications), in which some desired therapeutic effect is achieved, for example, the inhibition of the progress of the condition, and includes a reduction in the rate of progress, a halt in the rate of progress, regression of the condition, amelioration of the condition, and cure of the condition. Treatment as a prophylactic measure (i.e., prophylaxis, prevention) is also included.

The term “therapeutically-effective amount,” as used herein, pertains to that amount of an active compound, or a material, composition or dosage from comprising an active compound, which is effective for producing some desired therapeutic effect, commensurate with a reasonable benefit/risk ratio, when administered in accordance with a desired treatment regimen.

Similarly, the term “prophylactically-effective amount,” as used herein, pertains to that amount of an active compound, or a material, composition or dosage from comprising an active compound, which is effective for producing some desired prophylactic effect, commensurate with a reasonable benefit/risk ratio, when administered in accordance with a desired treatment regimen.

Preparation of Drug Conjugates

Antibody drug conjugates may be prepared by several routes, employing organic chemistry reactions, conditions, and reagents known to those skilled in the art, including reaction of a nucleophilic group of an antibody with a drug-linker reagent. This method may be employed to prepare the antibody-drug conjugates of the invention.

Nucleophilic groups on antibodies include, but are not limited to side chain thiol groups, e.g. cysteine. Thiol groups are nucleophilic and capable of reacting to form covalent bonds with electrophilic groups on linker moieties such as those of the present invention. Certain antibodies have reducible interchain disulfides, i.e. cysteine bridges. Antibodies may be made reactive for conjugation with linker reagents by treatment with a reducing agent such as DTT (Cleland's reagent, dithiothreitol) or TCEP (tris(2-carboxyethyl)phosphine hydrochloride; Getz et al (1999) Anal. Biochem. Vol 273:73-80; Soltec Ventures, Beverly, Mass.). Each cysteine disulfide bridge will thus form, theoretically, two reactive thiol nucleophiles. Additional nucleophilic groups can be introduced into antibodies through the reaction of lysines with 2-iminothiolane (Traut's reagent) resulting in conversion of an amine into a thiol.

The Subject/Patient

The subject/patient may be an animal, mammal, a placental mammal, a marsupial (e.g., kangaroo, wombat), a monotreme (e.g., duckbilled platypus), a rodent (e.g., a guinea pig, a hamster, a rat, a mouse), murine (e.g., a mouse), a lagomorph (e.g., a rabbit), avian (e.g., a bird), canine (e.g., a dog), feline (e.g., a cat), equine (e.g., a horse), porcine (e.g., a pig), ovine (e.g., a sheep), bovine (e.g., a cow), a primate, simian (e.g., a monkey or ape), a monkey (e.g., marmoset, baboon), an ape (e.g., gorilla, chimpanzee, orangutang, gibbon), or a human.

Furthermore, the subject/patient may be any of its forms of development, for example, a foetus. In one preferred embodiment, the subject/patient is a human.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows shows the effect on mean tumour volume in groups of 10 miced dosed with two different conjugates of the invention.

EXAMPLES

General Experimental Methods

Reaction progress was monitored by thin-layer chromatography (TLC) using Merck Kieselgel 60 F254 silica gel, with fluorescent indicator on aluminium plates. Visualisation of TLC was achieved with UV light or iodine vapour unless otherwise stated. Flash chromatography was performed using Merck Kieselgel 60 F254 silica gel. Extraction and chromatography solvents were bought and used without further purification from Fisher Scientific, U.K. All chemicals were purchased from Aldrich, Lancaster or BDH.

¹H and ¹³C NMR spectra were obtained on a Bruker Avance 400 spectrometer. Coupling constants are quoted in hertz (Hz). Chemical shifts are recorded in parts per million (ppm) downfield from tetramethylsilane. Spin multiplicities are described as s (singlet), bs (broad singlet), d (doublet), t (triplet), q (quartet), p (pentuplet) and m (multiplet). IR spectra were recorded on a Perkin-Elmer FT/IR paragon 1000 spectrophotometer by application of the sample in a solution of chloroform using the ATR “golden gate” system. Optical rotations were measured at ambient temperature using a Bellingham and Stanley ADP 220 polarimeter. Mass spectrometry was performed on a ThermoQuest Navigator from Thermo Electron, Electrospray (ES) spectra were obtained at 20 to 30 V. Accurate mass measurements were performed using Micromass Q-TOF global tandem. All samples were run under electrospray ionization mode using 50% acetonitrile in water and 0.1% formic acid as a solvent. Samples were run on W mode which gives a typical resolution of 19000 at FWHH. The instrument was calibrated with [Glu]-Fibrinopeptide B immediately prior to measurement.

LCMS

LC/MS (Shimazu LCMS-2020) using a mobile phase of water (A) (formic acid 0.1%) and acetonitrile (B) (formic acid 0.1%).

Gradient: initial composition 5% B held over 0.25 min, then increase from 5% B to 100% B over a 2 min period. The composition was held for 0.50 min at 100% B, then returned to 5% B in 0.05 minutes and hold there for 0.05 min. Total gradient run time equals 3 min. Flow rate 0.8 mL/min. Wavelength detection range: 190 to 800 nm. Oven temperature: 50° C. Column: Waters Acquity UPLC BEH Shield RP18 1.7 μm 2.1×50 mm.

Preparative HPLC

The conditions for the preparative HPLC were as follow: the HPLC (Shimadzu UFLC) was run using a mobile phase of water (0.1% formic acid) A and acetonitrile (0.1% formic acid) B. Wavelength detection range: 254 nm.

Column: Phenomenex Gemini 5μ C18 150×21-20 mm.

Gradient:

B t = 0 13% t = 15.00 95% t = 17.00 95% t = 17.10 13% t = 20.00 13%

Total gradient run time is 20 min; flow rate 20.00 mL/min.

Synthesis of Intermediate 12

(a) 1′,3′-Bis[2-methoxy-4-(methoxycarbonyl)phenoxy]propane (3)

Diisopropyl azodicarboxylate (71.3 mL, 73.2 g, 362 mmol) was added drop-wise over a period of 60 min to an overhead stirred solution of methyl vanillate 2 (60.0 g, 329 mmol) and Ph₃P (129.4 g, 494 mmol) in anhydrous THF (800 mL) at 0-5° C. (ice/acetone) under a nitrogen atmosphere. The reaction mixture was allowed to stir at 0-5° C. for an additional 1 hour after which time a solution of 1,3-propanediol (11.4 mL, 12.0 g, 158 mmol) in THF (12 mL) was added drop-wise over a period of 20 min. The reaction mixture was allowed to warm to room temperature and stirred for 5 days. The resulting white precipitate 3 was collected by vacuum filtration, washed with THF and dried in a vacuum desiccator to constant weight. Yield=54.7 g (84% based on 1,3-propanediol). Purity satisfactory by LC/MS (3.20 min (ES+) m/z (relative intensity) 427 ([M+Na]^(+.), 10); ¹H NMR (400 MHz, CDCl₃) δ 7.64 (dd, 2H, J=1.8, 8.3 Hz), 7.54 (d, 2H, J=1.8 Hz), 6.93 (d, 2H, J=8.5 Hz), 4.30 (t, 4H, J=6.1 Hz), 3.90 (s, 6H), 3.89 (s, 6H), 2.40 (p, 2H, J=6.0 Hz).

(b) 1′,3′-Bis[2-methoxy-4-(methoxycarbonyl)-5-nitrophenoxy]propane (4)

Solid Cu(NO₃)₂.3H₂O (81.5 g, 337.5 mmol) was added slowly to an overhead stirred slurry of the bis-ester 3 (54.7 g, 135 mmol) in acetic anhydride (650 mL) at 0-5° C. (ice/acetone). The reaction mixture was allowed to stir for 1 hour at 0-5° C. and then allowed to warm to room temperature. A mild exotherm (ca. 40-50° C.), accompanied by thickening of the mixture and evolution of NO₂ was observed at this stage. Additional acetic anhydride (300 mL) was added and the reaction mixture was allowed to stir for 16 hours at room temperature. The reaction mixture was poured on to ice (˜1.5 L), stirred and allowed to return to room temperature. The resulting yellow precipitate was collected by vacuum filtration and dried in a desiccator to afford the desired bis-nitro compound 4 as a yellow solid. Yield=66.7 g (100%). Purity satisfactory by LC/MS (3.25 min (ES+) m/z (relative intensity) 517 ([M+Na]^(+.), 40); ¹H NMR (400 MHz, CDCl₃) δ 7.49 (s, 2H), 7.06 (s, 2H), 4.32 (t, 4H, J=6.0 Hz), 3.95 (s, 6H), 3.90 (s, 6H), 2.45-2.40 (m, 2H).

(c) 1′,3′-Bis(4-carboxy-2-methoxy-5-nitrophenoxy) propane (5)

A slurry of the methyl ester 4 (66.7 g, 135 mmol) in THF (700 mL) was treated with 1N NaOH (700 mL) and the reaction mixture was allowed to stir vigorously at room temperature. After 4 days stirring, the slurry became a dark coloured solution which was subjected to rotary evaporation under reduced pressure to remove THF. The resulting aqueous residue was acidified to pH 1 with concentrated HCl and the colourless precipitate 5 was collected and dried thoroughly in a vacuum oven (50° C.). Yield=54.5 g (87%). Purity satisfactory by LC/MS (2.65 min (ES+) m/z (relative intensity) 489 ([M+Na]^(+.), 30)); ¹H NMR (400 MHz, DMSO-d₆) δ 7.62 (s, 2H), 7.30 (s, 2H), 4.29 (t, 4H, J=6.0 Hz), 3.85 (s, 6H), 2.30-2.26 (m, 2H).

(d) 1,1′-[[(Propane-1,3-diyl)dioxy]bis[(5-methoxy-2-nitro-1,4-phenylene)carbonyl]]bis[(2S,4R)-methyl-4-hydroxypyrrolidine-2-carboxylate] (6)

Oxalyl chloride (24.5 mL, 35.6 g, 281 mmol) was added to a stirred suspension of the nitrobenzoic acid 5 (43 g, 92.3 mmol) and DMF (6 mL) in anhydrous DCM (600 mL). Following initial effervescence the reaction suspension became a solution and the mixture was allowed to stir at room temperature for 16 hours. Conversion to the acid chloride was confirmed by treating a sample of the reaction mixture with MeOH and the resulting bis-methyl ester was observed by LC/MS. The majority of solvent was removed by evaporation under reduced pressure; the resulting concentrated solution was re-dissolved in a minimum amount of dry DCM and triturated with diethyl ether. The resulting yellow precipitate was collected by filtration, washed with cold diethyl ether and dried for 1 hour in a vacuum oven at 40° C. The solid acid chloride was added portionwise over a period of 25 min to a stirred suspension of (2S,4R)-methyl-4-hydroxypyrrolidine-2-carboxylate hydrochloride (38.1 g, 210 mmol) and TEA (64.5 mL, g, 463 mmol) in DCM (400 mL) at −40° C. (dry ice/CH₃CN). Immediately, the reaction was complete as judged by LC/MS (2.47 min (ES+) m/z (relative intensity) 721 ([M+H]^(+.), 100). The mixture was diluted with DCM (200 mL) and washed with 1N HCl (300 mL), saturated NaHCO₃ (300 mL), brine (400 mL), dried (MgSO₄), filtered and the solvent evaporated in vacuo to give the pure product 6 as an orange solid (66.7 g, 100%). [α]²² _(D)=−46.1° (c=0.47, CHCl₃); ¹H NMR (400 MHz, CDCl₃) (rotamers) δ 7.63 (s, 2H), 6.82 (s, 2H), 4.79-4.72 (m, 2H), 4.49-4.28 (m, 6H), 3.96 (s, 6H), 3.79 (s, 6H), 3.46-3.38 (m, 2H), 3.02 (d, 2H, J=11.1 Hz), 2.48-2.30 (m, 4H), 2.29-2.04 (m, 4H); ¹³C NMR (100 MHz, CDCl₃) (rotamers) δ 172.4, 166.7, 154.6, 148.4, 137.2, 127.0, 109.7, 108.2, 69.7, 65.1, 57.4, 57.0, 56.7, 52.4, 37.8, 29.0; IR (ATR, CHCl₃) 3410 (br), 3010, 2953, 1741, 1622, 1577, 1519, 1455, 1429, 1334, 1274, 1211, 1177, 1072, 1050, 1008, 871 cm⁻¹; MS (ES⁺) m/z (relative intensity) 721 ([M+H]^(+.), 47), 388 (80); HRMS [M+H]^(+.) theoretical C₃₁H₃₆N₄O₁₆ m/z 721.2199, found (ES⁺) m/z 721.2227.

(e) 1,1′-[[(Propane-1,3-diyl)dioxy]bis(11aS,2R)-2-(hydroxy)-7-methoxy-1,2,3,10,11,11a-hexahydro-5H-pyrrolo[2,1-c][1,4]-benzodiazepin-5,11-dione] (7)

Method A: A solution of the nitro-ester 6 (44 g, 61.1 mmol) in MeOH (2.8 L) was added to freshly purchased Raney® nickel (˜50 g of a ˜50% slurry in H₂O) and anti-bumping granules in a 5 L 3-neck round bottomed flask. The mixture was heated at reflux and then treated dropwise with a solution of hydrazine hydrate (21.6 mL, 22.2 g, 693 mmol) in MeOH (200 mL) at which point vigorous effervescence was observed. When the addition was complete (˜45 min) additional Raney® nickel was added carefully until effervescence had ceased and the initial yellow colour of the reaction mixture was discharged. The mixture was heated at reflux for a further 5 min at which point the reaction was deemed complete by TLC (90:10 v/v CHCl₃/MeOH) and LC/MS (2.12 min (ES+) m/z (relative intensity) 597 ([M+H]^(+.), 100)). The reaction mixture was filtered hot immediately through a sinter funnel containing celite with vacuum suction. The filtrate was reduced in volume by evaporation in vacuo at which point a colourless precipitate formed which was collected by filtration and dried in a vacuum desiccator to provide 7 (31 g, 85%). [α]²⁷ _(D)=+404° (c=0.10, DMF); ¹H NMR (400 MHz, DMSO-d₆) δ 10.2 (s, 2H, NH), 7.26 (s, 2H), 6.73 (s, 2H), 5.11 (d, 2H, J=3.98 Hz, OH), 4.32-4.27 (m, 2H), 4.19-4.07 (m, 6H), 3.78 (s, 6H), 3.62 (dd, 2H, J=12.1, 3.60 Hz), 3.43 (dd, 2H, J=12.0, 4.72 Hz), 2.67-2.57 (m, 2H), 2.26 (p, 2H, J=5.90 Hz), 1.99-1.89 (m, 2H); ¹³C NMR (100 MHz, DMSO-d₆) δ 169.1, 164.0, 149.9, 144.5, 129.8, 117.1, 111.3, 104.5, 54.8, 54.4, 53.1, 33.5, 27.5; IR (ATR, neat) 3438, 1680, 1654, 1610, 1605, 1516, 1490, 1434, 1379, 1263, 1234, 1216, 1177, 1156, 1115, 1089, 1038, 1018, 952, 870 cm⁻¹; MS (ES⁺) m/z (relative intensity) 619 ([M+Na]^(+.), 10), 597 ([M+H]^(+.), 52), 445 (12), 326 (11); HRMS [M+H]^(+.) theoretical C₂₉H₃₂N₄O₁₀ m/z 597.2191, found (ES⁺) m/z 597.2205.

Method B: A suspension of 10% Pd/C (7.5 g, 10% w/w) in DMF (40 mL) was added to a solution of the nitro-ester 6 (75 g, 104 mmol) in DMF (360 mL). The suspension was hydrogenated in a Parr hydrogenation apparatus over 8 hours. Progress of the reaction was monitored by LC/MS after the hydrogen uptake had stopped. Solid Pd/C was removed by filtration and the filtrate was concentrated by rotary evaporation under vacuum (below 10 mbar) at 40° C. to afford a dark oil containing traces of DMF and residual charcoal. The residue was digested in EtOH (500 mL) at 40° C. on a water bath (rotary evaporator bath) and the resulting suspension was filtered through celite and washed with ethanol (500 mL) to give a clear filtrate. Hydrazine hydrate (10 mL, 321 mmol) was added to the solution and the reaction mixture was heated at reflux. After 20 minutes the formation of a white precipitate was observed and reflux was allowed to continue for a further 30 minutes. The mixture was allowed to cool down to room temperature and the precipitate was retrieved by filtration, washed with diethyl ether (2:1 volume of precipitate) and dried in a vacuum desiccator to provide 7 (50 g, 81%). Analytical data for method B: Identical to those obtained for Method A (optical rotation, ¹H NMR, LC/MS and TLC).

(f) 1,1′-[[(Propane-1,3-diyl)dioxy]bis(11aS,2R)-2-(tert-butyldimethylsilyloxy)-7-methoxy-1,2,3,10,11,11a-hexahydro-5H-pyrrolo[2,1-c][1,4]-benzodiazepin-5,11-dione] (8)

TBSCl (27.6 g, 182.9 mmol) and imidazole (29.9 g, 438.8 mmol) were added to a cloudy solution of the tetralactam 7 (21.8 g, 36.6 mmol) in anhydrous DMF (400 mL) at 0° C. (ice/acetone). The mixture was allowed to stir under a nitrogen atmosphere for 3 hours after which time the reaction was deemed complete as judged by LC/MS (3.90 min (ES+) m/z (relative intensity) 825 ([M+H]^(+.), 100). The reaction mixture was poured onto ice (˜1.75 L) and allowed to warm to room temperature with stirring. The resulting white precipitate was collected by vacuum filtration, washed with H₂O, diethyl ether and dried in the vacuum desicator to provide pure 8 (30.1 g, 99%). [α]²³ _(D)=+234° (c=0.41, CHCl₃); ¹H NMR (400 MHz, CDCl₃) δ 8.65 (s, 2H, NH), 7.44 (s, 2H), 6.54 (s, 2H), 4.50 (p, 2H, J=5.38 Hz), 4.21-4.10 (m, 6H), 3.87 (s, 6H), 3.73-3.63 (m, 4H), 2.85-2.79 (m, 2H), 2.36-2.29 (m, 2H), 2.07-1.99 (m, 2H), 0.86 (s, 18H), 0.08 (s, 12H); ¹³C NMR (100 MHz, CDCl₃) δ 170.4, 165.7, 151.4, 146.6, 129.7, 118.9, 112.8, 105.3, 69.2, 65.4, 56.3, 55.7, 54.2, 35.2, 28.7, 25.7, 18.0, −4.82 and −4.86; IR (ATR, CHCl₃) 3235, 2955, 2926, 2855, 1698, 1695, 1603, 1518, 1491, 1446, 1380, 1356, 1251, 1220, 1120, 1099, 1033 cm⁻¹; MS (ES⁺) m/z (relative intensity) 825 ([M+H]^(+.), 62), 721 (14), 440 (38); HRMS [M+H]^(+.) theoretical C₄₁H₆₀N₄O₁₀Si₂ m/z 825.3921, found (ES⁺) m/z 825.3948.

(g) 1,1′-[[(Propane-1,3-diyl)dioxy]bis(11aS,2R)-2-(tert-butyldimethylsilyloxy)-7-methoxy-10-((2-(trimethylsilyl)ethoxy)methyl)-1,2,3,10,11,11a-hexahydro-5H-pyrrolo[2,1-c][1,4]-benzodiazepin-5,11-dione] (9)

A solution of n-BuLi (68.3 mL of a 1.6 M solution in hexane, 109 mmol) was added dropwise to a stirred suspension of the tetralactam 8 (30.08 g, 36.4 mmol) in anhydrous THF (600 mL) at −30° C. (dry ice/ethylene glycol) under a nitrogen atmosphere. The reaction mixture was allowed to stir at this temperature for 1 hour (now a reddish orange colour) at which point a solution of SEMCl (19.3 mL, 18.2 g, 109 mmol) in anhydrous THF (120 mL) was added dropwise. The reaction mixture was allowed to slowly warm to room temperature and was stirred for 16 hours under a nitrogen atmosphere. The reaction was deemed complete as judged by TLC (EtOAc) and LC/MS (4.77 min (ES+) m/z (relative intensity) 1085 ([M+H]^(+.), 100). The THF was removed by evaporation in vacuo and the resulting residue dissolved in EtOAc (750 mL), washed with H₂O (250 mL), brine (250 mL), dried (MgSO₄) filtered and evaporated in vacuo to provide the crude N10-SEM-protected tetralactam 9 as an oil (max^(m) 39.5 g, 100%). Product carried through to next step without purification. [α]²³ _(D)=+163° (c=0.41, CHCl₃); ¹H NMR (400 MHz, CDCl₃) δ 7.33 (s, 2H), 7.22 (s, 2H), 5.47 (d, 2H, J=9.98 Hz), 4.68 (d, 2H, J=9.99 Hz), 4.57 (p, 2H, J=5.77 Hz), 4.29-4.19 (m, 6H), 3.89 (s, 6H), 3.79-3.51 (m, 8H), 2.87-2.81 (m, 2H), 2.41 (p, 2H, J=5.81 Hz), 2.03-1.90 (m, 2H), 1.02-0.81 (m, 22H), 0.09 (s, 12H), 0.01 (s, 18H); ¹³C NMR (100 MHz, CDCl₃) δ 170.0, 165.7, 151.2, 147.5, 133.8, 121.8, 111.6, 106.9, 78.1, 69.6, 67.1, 65.5, 56.6, 56.3, 53.7, 35.6, 30.0, 25.8, 18.4, 18.1, −1.24, −4.73; IR (ATR, CHCl₃) 2951, 1685, 1640, 1606, 1517, 1462, 1433, 1360, 1247, 1127, 1065 cm⁻¹; MS (ES⁺) m/z (relative intensity) 1113 ([M+Na]^(+.), 48), 1085 ([M+H]^(+.), 100), 1009 (5), 813 (6); HRMS [M+H]^(+.) theoretical C₅₃H₈₈N₄O₁₂Si₄ m/z 1085.5548, found (ES⁺) m/z 1085.5542.

(h) 1,1′-[[(Propane-1,3-diyl)dioxy]bis(11aS,2R)-2-hydroxy-7-methoxy-10-((2-(trimethylsilyl)ethoxy)methyl)-1,2,3,10,11,11a-hexahydro-5H-pyrrolo[2,1-c][1,4]-benzodiazepin-5,11-dione] (10)

A solution of TBAF (150 mL of a 1.0 M solution in THF, 150 mmol) was added to a stirred solution of the crude bis-silyl ether 9 [84.0 g (max^(m) 56.8 g), 52.4 mmol] in THF (800 mL) at room temperature. After stirring for 1 hour, analysis of the reaction mixture by TLC (95:5 v/v CHCl₃/MeOH) revealed completion of reaction. The THF was removed by evaporation under reduced pressure at room temperature and the resulting residue dissolved in EtOAc (500 mL) and washed with NH₄Cl (300 mL). The combined organic layers were washed with brine (60 mL), dried (MgSO₄), filtered and evaporated under reduced pressure to provide the crude product. Purification by flash chromatography (gradient elution: 100% CHCl₃ to 96:4 v/v CHCl₃/MeOH) gave the pure tetralactam 10 as a white foam (36.0 g, 79%). LC/MS 3.33 min (ES+) m/z (relative intensity) 879 ([M+Na]^(+.), 100), 857 ([M+H]^(+.), 40); [α]²³ _(D)=+202° (c =0.34, CHCl₃); ¹H NMR (400 MHz, CDCl₃) δ 7.28 (s, 2H), 7.20 (s, 2H), 5.44 (d, 2H, J=10.0 Hz), 4.72 (d, 2H, J=10.0 Hz), 4.61-4.58 (m, 2H), 4.25 (t, 4H, J=5.83 Hz), 4.20-4.16 (m, 2H), 3.91-3.85 (m, 8H), 3.77-3.54 (m, 6H), 3.01 (br s, 2H, OH), 2.96-2.90 (m, 2H), 2.38 (p, 2H, J=5.77 Hz), 2.11-2.05 (m, 2H), 1.00-0.91 (m, 4H), 0.00 (s, 18H); ¹³C NMR (100 MHz, CDCl₃) δ 169.5, 165.9, 151.3, 147.4, 133.7, 121.5, 111.6, 106.9, 79.4, 69.3, 67.2, 65.2, 56.5, 56.2, 54.1, 35.2, 29.1, 18.4, −1.23; IR (ATR, CHCl₃) 2956, 1684, 1625, 1604, 1518, 1464, 1434, 1361, 1238, 1058, 1021 cm⁻¹; MS (ES⁺) m/z (relative intensity) 885 ([M+29]^(+.), 70), 857 ([M+H]^(+.), 100), 711 (8), 448 (17); HRMS [M+H]^(+.) theoretical C₄₁H₆₀N₄O₁₂Si₂ 857.3819, found (ES⁺) m/z 857.3826.

(i) 1,1′-[[(Propane-1,3-diyl)dioxy]bis(11aS)-7-methoxy-2-oxo-10-((2-(trimethylsilyl)ethoxy)methyl)-1,2,3,10,11,11a-hexahydro-5H-pyrrolo[2,1-c][1,4]-benzodiazepin-5,11-dione] (11)

Diol 10 (25.6 g, 30 mmol, 1 eq.), NaOAc (6.9 g, 84 mmol, 2.8 eq.) and TEMPO (188 mg, 1.2 mmol, 0.04 eq.) were dissolved in DCM (326 mL) under Ar. This was cooled to −8° C. (internal temperature) and TCCA (9.7 g, 42 mmol, 1.4 eq.) was added portionwise over 15 minutes. TLC (EtOAc) and LC/MS [3.60 min. (ES+) m/z (relative intensity) 854.21 ([M+H]^(+.), 40), (ES−) m/z (relative intensity) 887.07 ([M−H+Cl]^(−.), 10)] after 30 minutes indicated that reaction was complete. Cold DCM (200 mL) was added and the mixture was filtered through a pad of Celite before washing with a solution of saturated sodium hydrogen carbonate/sodium thiosulfate (1:1 v/v; 200 mL×2). The organic layer was dried with MgSO₄, filtered and the solvent removed in vacuo to yield a yellow/orange sponge (25.4 g, 99%). LC/MS [3.60 min. (ES+) m/z (relative intensity) 854.21 ([M+H]^(+.), 40); [α]²⁰ _(D)=+291° (c=0.26, CHCl₃); ¹H NMR (400 MHz, CDCl₃) δ 7.32 (s, 2H), 7.25 (s, 2H), 5.50 (d, 2H, J=10.1 Hz), 4.75 (d, 2H, J=10.1 Hz), 4.60 (dd, 2H, J=9.85, 3.07 Hz), 4.31-4.18 (m, 6H), 3.89-3.84 (m, 8H), 3.78-3.62 (m, 4H), 3.55 (dd, 2H, J=19.2, 2.85 Hz), 2.76 (dd, 2H, J=19.2, 9.90 Hz), 2.42 (p, 2H, J=5.77 Hz), 0.98-0.91 (m, 4H), 0.00 (s, 18H); ¹³C NMR (100 MHz, CDCl₃) δ 206.8, 168.8, 165.9, 151.8, 148.0, 133.9, 120.9, 111.6, 107.2, 78.2, 67.3, 65.6, 56.3, 54.9, 52.4, 37.4, 29.0, 18.4, −1.24; IR (ATR, CHCl₃) 2957, 1763, 1685, 1644, 1606, 1516, 1457, 1434, 1360, 1247, 1209, 1098, 1066, 1023 cm⁻¹; MS (ES⁺) m/z (relative intensity) 881 ([M+29]^(+.), 38), 853 ([M+H]^(+.), 100), 707 (8), 542 (12); HRMS [M+H]^(+.) theoretical C₄₁H₅₆N₄O₁₂Si₂ 853.3506, found (ES⁺) m/z 853.3502.

(j) 1,1′-[[(Propane-1,3-diyl)dioxy]bis(11aS)-7-methoxy-2-[[(trifluoromethyl)sulfonyl]oxy]-10-((2-(trimethylsilyl)ethoxy)methyl)-1,10,11,11a-tetrahydro-5H-pyrrolo[2,1-c][1,4]-benzodiazepin-5,11-dione] (12)

Anhydrous 2,6-lutidine (5.15 mL, 4.74 g, 44.2 mmol) was injected in one portion to a vigorously stirred solution of bis-ketone 11 (6.08 g, 7.1 mmol) in dry DCM (180 mL) at −45° C. (dry ice/acetonitrile) under a nitrogen atmosphere. Anhydrous triflic anhydride, taken from a freshly opened ampoule (7.2 mL, 12.08 g, 42.8 mmol), was injected rapidly dropwise, while maintaining the temperature at −40° C. or below. The reaction mixture was allowed to stir at −45° C. for 1 hour at which point TLC (50/50 v/v n-hexane/EtOAc) revealed the complete consumption of starting material. The cold reaction mixture was immediately diluted with DCM (200 mL) and, with vigorous shaking, washed with water (1×100 mL), 5% citric acid solution (1×200 mL) saturated NaHCO₃ (200 mL), brine (100 mL) and dried (MgSO₄). Filtration and evaporation of the solvent under reduced pressure afforded the crude product which was purified by flash column chromatography (gradient elution: 90:10 v/v n-hexane/EtOAc to 70:30 v/v n-hexane/EtOAc) to afford bis-enol triflate 12 as a yellow foam (5.5 g, 70%). LC/MS 4.32 min (ES+) m/z (relative intensity) 1139 ([M+Na]^(+.), 20); [α]²⁴ _(D)=+271° (c=0.18, CHCl₃); ¹H NMR (400 MHz, CDCl₃) δ 7.33 (s, 2H), 7.26 (s, 2H), 7.14 (t, 2H, J=1.97 Hz), 5.51 (d, 2H, J=10.1 Hz), 4.76 (d, 2H, J=10.1 Hz), 4.62 (dd, 2H, J=11.0, 3.69 Hz), 4.32-4.23 (m, 4H), 3.94-3.90 (m, 8H), 3.81-3.64 (m, 4H), 3.16 (ddd, 2H, J=16.3, 11.0, 2.36 Hz), 2.43 (p, 2H, J=5.85 Hz), 1.23-0.92 (m, 4H), 0.02 (s, 18H); ¹³C NMR (100 MHz, CDCl₃) δ 167.1, 162.7, 151.9, 148.0, 138.4, 133.6, 120.2, 118.8, 111.9, 107.4, 78.6, 67.5, 65.6, 56.7, 56.3, 30.8, 29.0, 18.4, −1.25; IR (ATR, CHCl₃) 2958, 1690, 1646, 1605, 1517, 1456, 1428, 1360, 1327, 1207, 1136, 1096, 1060, 1022, 938, 913 cm⁻¹; MS (ES⁺) m/z (relative intensity) 1144 ([M+28]^(+.), 100), 1117 ([M+H]^(+.), 48), 1041 (40), 578 (8); HRMS [M +H]^(+.) theoretical C₄₃H₅₄N₄O₁₆Si₂S₂F₆ m/z 1117.2491, found (ES⁺) m/z 1117.2465.

Synthesis of Intermediate 15

(a) (R)-2-((R)-2-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)-3-methylbutanamido) propanoic acid (14)

HO-Ala-Val-H 13 (350 mg, 1.86 mmol) and Na₂CO₃ (493 mg, 4.65 mmol) were dissolved in distilled H₂O (15 mL) and the mixture was cooled to 0° C. before dioxane (15 mL) was added (partial precipitation of the amino acid salt occurred). A solution of Fmoc-Cl (504 mg, 1.95 mmol) in dioxane (15 mL) was added dropwise with vigorous stirring over 10 minutes. The resulting mixture was stirred at 0° C. for 2 hours before the ice bath was removed and stirring was maintained for 16 hours. The solvent was removed by rotary evaporation under reduced pressure and the residue dissolved in water (150 mL). The pH was adjusted from 9 to 2 with 1N HCl and the aqueous layer was subsequently extracted with EtOAc (3×100 mL). The combined organics were washed with brine (100 mL), dried with MgSO₄, filtered and the volatiles removed by rotary evaporation under reduced pressure to afford pure HO-Ala-Val-Fmoc 14 (746 mg, 97% yield). LC/MS 2.85 min (ES+) m/z (relative intensity) 410.60; ¹H-NMR (400 MHz, CDCl₃) δ 7.79 (d, J=7.77 Hz, 2H), 7.60 (d, J=7.77 Hz, 2H), 7.43 (d, J=7.5 Hz, 2H), 7.34 (d, J=7.5 Hz, 2H), 6.30 (bs, 1H), 5.30 (bs, 1H), 4.71-7.56 (m, 1H), 4.54-4.36 (m, 2H), 4.08-3.91 (m, 1H), 2.21-2.07 (m, 1H), 1.50 (d, J=7.1 Hz, 3H), 1.06-0.90 (m, 6H).

(b) (9H-fluoren-9-yl)methyl ((S)-3-methyl-1-oxo-1-(((S)-1-oxo-1-((4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)amino)propan-2-yl)amino)butan-2-yl)carbamate (15)

4-Aminophenylboronic acid pinacol ester was added (146.9 mg, 0.67 mmol) was added to a solution of HO-Ala-Val-Fmoc 14 (330 mg, 0.8 mmol), DCC (166 mg, 0.8 mmol) and DMAP (5 mg, cat.) in dry DCM (8 mL) previously stirred for 30 minutes at room temperature in a flask flushed with argon. The reaction mixture was then allowed to stir at room temperature overnight. The reaction was followed by LCMS and TLC. The reaction mixture was diluted with CH₂Cl₂ and the organics were washed with H₂O and brine before being dried with MgSO₄, filtered and the solvent removed by rotary evaporation under reduced pressure. The crude product was dryloaded on a silicagel chromatography column (Hexane/EtOAc, 6:4) and pure product 15 was isolated as a white solid in 88% yield (360 mg).

Example 1

(a) (S)-7-methoxy-8-(3-(((S)-7-methoxy-2-(4-(4-methylpiperazin-1-yl)phenyl)-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a-tetrahydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-8-yl)oxy)propoxy)-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a-tetrahydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-2-yl trifluoromethanesulfonate (16)

Pd(PPh₃)₄ (20.6 mg, 0.018 mmol) was added to a stirred mixture of the bis-enol triflate 12 (500 mg, 0.44 mmol), N-methyl piperazine boronic ester (100 mg, 0.4 mmol), Na₂CO₃ (218 mg, 2.05 mmol), MeOH (2.5 mL), toluene (5 mL) and water (2.5 mL). The reaction mixture was allowed to stir at 30° C. under a nitrogen atmosphere for 24 hours after which time all the boronic ester has consumed. The reaction mixture was then evaporated to dryness before the residue was taken up in EtOAc (100 mL) and washed with H₂O (2×50 mL), brine (50 mL), dried (MgSO₄), filtered and evaporated under reduced pressure to provide the crude product. Purification by flash chromatography (gradient elution: 80:20 v/v Hexane/EtOAc to 60:40 v/v Hexane/EtOAc) afforded product 16 as a yellowish foam (122.6 mg, 25%). LC/MS 3.15 min (ES+) m/z (relative intensity) 1144 ([M+H]^(+.), 20%).

(b) (9H-fluoren-9-yl)methyl ((S)-1-(((S)-1-((4-((S)-7-methoxy-8-(3-(((S)-7-methoxy-2-(4-(4-methylpiperazin-1-yl)phenyl)-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a-tetrahydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-8-yl)oxy)propoxy)-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a-tetrahydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)amino)-3-methyl-1-oxobutan-2-yl)carbamate (17)

PBD-triflate 16 (359 mg, 0.314 mmol), boronic pinacol ester 15 (250 mg, 0.408 mmol) and triethylamine (0.35 mL, 2.51 mmol) were dissolved in a mixture of toluene/MeOH/H₂O, 2:1:1 (3 mL). The microwave vessel was purged and filled with argon three times before tetrakis(triphenylphosphine)palladium(0) (21.7 mg, 0.018 mmol) was added and the reaction mixture placed in the microwave at 80° C. for 10 minutes. Subsequently, CH₂Cl₂ (100 mL) was added and the organics were washed with water (2×50 mL) and brine (50 mL) before being dried with MgSO₄, filtered and the volatiles removed by rotary evaporation under reduced pressure. The crude product was purified by silica gel chromatography column (CHCl₃/MeOH, 100% to 9:1) to afford pure 17 (200 mg, 43% yield). LC/MS 3.27 min (ES+) m/z (relative intensity) 1478 ([M+H]^(+.), 100%).

(c) (9H-fluoren-9-yl)methyl ((S)-1-(((S)-1-((4-((S)-7-methoxy-8-(3-(((S)-7-methoxy-2-(4-(4-methyl piperazin-1-yl)phenyl)-5-oxo-5,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-8-yl)oxy)propoxy)-5-oxo-5,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)amino)-3-methyl-1-oxobutan-2-yl)carbamate (18)

A solution of Super-Hydride® (0.34 mL, 1M in THF) was added dropwise to a solution of SEM-dilactam 17 (200 mg, 0.135 mmol) in THF (5 mL) at −78° C. under an argon atmosphere. The addition was completed over 5 minutes in order to maintain the internal temperature of the reaction mixture constant. After 20 minutes, an aliquot was quenched with water for LC/MS analysis, which revealed that the reaction was complete. Water (20 mL) was added to the reaction mixture and the cold bath was removed. The organic layer was extracted with EtOAc (3×30 mL) and the combined organics were washed with brine (50 mL), dried with MgSO₄, filtered and the solvent removed by rotary evaporation under reduced pressure. The crude product was dissolved in MeOH (6 mL), CH₂Cl₂ (3 mL), water (1 mL) and enough silica gel to form a thick stirring suspension. After 5 days, the suspension was filtered through a sintered funnel and washed with CH₂Cl₂/MeOH (9:1) (100 mL) until the elution of the product was complete. The organic layer was washed with brine (2×50 mL), dried with MgSO₄, filtered and the solvent removed by rotary evaporation under reduced pressure. Purification by silica gel column chromatography (100% CHCl₃ to 96% CHCl₃/4% MeOH) afforded the product 18 as a yellow solid (100 mg, 63%). LC/MS 2.67 min (ES+) m/z (relative intensity) 1186 ([M+H]^(+.), 5%).

(d) (S)-2-amino-N—((S)-1-((4-((R)-7-methoxy-8-(3-(((R)-7-methoxy-2-(4-(4-methylpiperazin-1-yl)phenyl)-5-oxo-5,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-8-yl)oxy)propoxy)-5-oxo-5,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)-3-methylbutanamide (19)

Excess piperidine was added (0.1 mL, 1 mmol) to a solution of PBD 18 (36.4 mg, 0.03 mmol) in DMF (0.9 mL). The mixture was allowed to stir at room temperature for 20 min, at which point the reaction had gone to completion (as monitored by LC/MS). The reaction mixture was diluted with CH₂Cl₂ (50 mL) and the organic phase was washed with H₂O (3×50 mL) until complete piperidine removal. The organic phase was dried over MgSO₄, filtered and excess solvent removed by rotary evaporation under reduced pressure to afford crude product 19 which was used as such in the next step. LC/MS 2.20 min (ES+) m/z (relative intensity) 964 ([M+H]^(+.), 5%).

(e) 1-(3-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)propanamido)-N-((2S)-1-(((2S)-1-((4-(7-methoxy-8-(3-((7-methoxy-2-(4-(4-methylpiperazin-1-yl)phenyl)-5-oxo-5,11a-dihydro-1H-benzo [e]pyrrolo[1,2-a][1,4]diazepin-8-yl)oxy)propoxy)-5-oxo-5,11a-dihydro-1H-benzo [e]pyrrolo[1,2-a][1,4]diazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)amino)-3-methyl-1-oxobutan-2-yl)-3,6,9,12,15,18,21,24-octaoxaheptacosan-27-amide (20)

EDCl hydrochloride (8 mg, 0.042 mmol) was added to a suspension of Maleimide-PEG₈-acid (25 mg, 0.042 mmol) in dry CH₂Cl₂ (4 mL) under argon atmosphere. PBD 19 (42 mg, crude) was added straight away and stirring was maintained until the reaction was complete (3 hours). The reaction was diluted with CH₂Cl₂ and the organic phase was washed with H₂O and brine before being dried over MgSO₄, filtered and excess solvent removed by rotary evaporation under reduced pressure by rotary evaporation under reduced pressure. The product was purified by careful silica gel chromatography (slow elution starting with 100% CHCl₃ up to 9:1 CHCl₃/MeOH) followed by reverse phase HPLC to remove unreacted maleimide-PEG₈-acid. The product 20 was isolated in 10% over two steps (6.6 mg). LC/MS 1.16 min (ES+) m/z (relative intensity) 770.20 ([M+2H]^(+.), 40%).

Example 2 Alternative Synthesis of Compound 17

(a) 8-(3-((2-(4-((S)-2-((S)-2-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)-3-methylbutanamido)propanamido)phenyl)-7-methoxy-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a-tetrahydro-H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yl)oxy)propoxy)-7-methoxy-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a-tetrahydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-2-yl trifluoromethanesulfonate (21)

Bis-triflate 12 (2.03 g, 1.81 mmol), boronic pinacol ester 20 (1 g, 1.63 mmol) and Na₂CO₃ (881 mg, 8.31 mmol) were dissolved in a mixture of toluene/MeOH/H₂O, 2:1:1 (40 mL). The reaction flask was purged and filled with argon three times before tetrakis(triphenylphosphine)palladium(0) (41 mg, 0.035 mmol) was added and the reaction mixture heated to 30° C. overnight. The solvents were removed under reduce pressure and the residue was taken up in H₂O (100 mL) and extracted with EtOAc (3×100 mL). The combined organics were washed with brine (100 mL), dried with MgSO₄, filtered and the volatiles removed by rotary evaporation under reduced pressure. The crude product was purified by silica gel chromatography column (Hexane/EtOAc, 8:2 to 25:75) to afford pure 21 in 33% yield (885 mg). LC/MS 3.85 min (ES+) m/z (relative intensity) 1452.90; ¹H NMR (400 MHz, CDCl₃) δ 7.78-7.16 (m, 17H), 7.13 (s, 1H), 6.51-6.24 (m, 1H), 5.51 (dd, J=10.0, 5.1 Hz, 2H), 5.36-5.11 (m, 1H), 4.74 (dd, J=10.1, 4.4 Hz, 2H), 4.70-4.53 (m, 2H), 4.47 (d, J=6.4 Hz, 1H), 4.37 (d, J=7.2 Hz, 1H), 4.27 (m, 4H), 4.20-4.14 (m, 1H), 3.90 (s, 3H), 3.89 (s, 3H), 3.77 (ddd, J=16.7, 9.0, 6.4 Hz, 3H), 3.71-3.61 (m, 2H), 3.24-2.91 (m, 3H), 2.55-2.33 (m, 2H), 2.22-2.07 (m, 1H), 1.52-1.37 (m, 3H), 1.04-0.86 (m, 10H), 0.00 (s, 18H).

(b) (9H-fluoren-9-yl)methyl ((S)-1-(((S)-1-((4-((S)-7-methoxy-8-(3-(((S)-7-methoxy-2-(4-(4-methylpiperazin-1-yl)phenyl)-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a-tetrahydro -H-pyrrolo[2,1-c][1,4]benzodiazepin-8-yl)oxy)propoxy)-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a-tetrahydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)amino)-3-methyl-1-oxobutan-2-yl)carbamate (17)

PBD-triflate 21 (469 mg, 0.323 mmol), boronic pinacol ester (146.5 mg, 0.484 mmol) and Na₂CO₃ (157 mg, 1.48 mmol) were dissolved in a mixture of toluene/MeOH/H₂O, 2:1:1 (10 mL). The reaction flask was purged with argon three times before tetrakis(triphenylphosphine)palladium(0) (7.41 mg, 0.0064 mmol) was added and the reaction mixture heated to 30° C. overnight. The solvents were removed under reduced pressure and the residue was taken up in H₂O (50 mL) and extracted with EtOAc (3×50 mL). The combined organics were washed with brine (100 mL), dried with MgSO₄, filtered and the volatiles removed by rotary evaporation under reduced pressure. The crude product was purified by silica gel column chromatography (CHCl₃ 100% to CHCl₃/MeOH 95%:5%) to afford pure 17 in 33% yield (885 mg). LC/MS 3.27 min (ES+) m/z (relative intensity) 1478 ([M+H]^(+.), 100%).

Example 3

(a) (S)-7-methoxy-8-((5-(((S)-7-methoxy-2-(4-(4-methypiperazin-1-yl)phenyl)-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a-tetrahydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yl)oxy)pentyl)oxy)-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a-tetrahydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-2-yl trifluoromethanesulfonate (23)

Pd(PPh₃)₄ (30 mg, 26 μmol) was added to a stirred mixture of the bis-enol triflate 22 (1 g, 0.87 mmol), 4-(4-methylpiperazin-1-yl)phenylboronic acid, pinacol ester (264 mg, 0.87 mmol), Na₂CO₃ (138 mg, 1.30 mmol), EtOH (5 mL), toluene (10 mL) and water (5 mL). The reaction mixture was allowed to stir under a nitrogen atmosphere overnight at room temperature after which time the complete consumption of starting material was observed by TLC (EtOAc) and LC/MS (1.52 min (ES+) m/z (relative intensity) 1171.40 ([M+H]^(+.), 100)). The reaction mixture was diluted with EtOAc (400 mL) and washed with H₂O (2×300 mL), brine (200 mL), dried (MgSO₄), filtered and evaporated under reduced pressure to provide the crude product. Purification by flash chromatography (gradient elution: 100:0 v/v EtOAc/MeOH to 85:15 v/v EtOAc/MeOH) afforded the asymmetrical triflate 23 (285 mg, 28%). ¹H NMR (400 MHz, CDCl3) δ 7.39 (s, 1H), 7.37-7.29 (m, 4H), 7.23 (d, J=2.8 Hz, 2H), 7.14 (t, J=2.0 Hz, 1H), 6.89 (d, J=9.0 Hz, 2H), 5.54 (d, J=10.0 Hz, 2H), 4.71 (dd, J=10.0, 2.6 Hz, 2H), 4.62 (td, J=10.7, 3.5 Hz, 2H), 4.13-4.01 (m, 4H), 3.97-3.87 (m, 8H), 3.85-3.75 (m, 2H), 3.74-3.63 (m, 2H), 3.31-3.22 (m, 4H), 3.14 (tdd, J=16.2, 10.8, 2.2 Hz, 2H), 2.73-2.56 (m, 4H), 2.38 (d, J=2.4 Hz, 3H), 2.02-1.92 (m, 4H), 1.73 (dd, J=9.4, 6.0 Hz, 2H), 1.04-0.90 (m, 4H), 0.05-−0.00 (m, 18H). MS (ES⁺) m/z (relative intensity) 1171.40 ([M+H]^(+.), 100).

(b) (9H-fluoren-9-yl)methyl ((S)-1-(((S)-1-((4-((S)-7-methoxy-8-((5-(((S)-7-methoxy-2-(4-(4-methylpiperazin-1-yl)phenyl)-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a -tetrahydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yl)oxy)pentyl)oxy)-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a-tetrahydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)amino)-3-methyl-1-oxobutan-2-yl)carbamate (24)

Pd(PPh₃)₄ (8 mg, 7 μmol) was added to a stirred mixture of the asymmetrical triflate 23 (269 mg, 0.23 mmol), Fmoc-Val-Ala-4-aminophenylboronic acid, pinacol ester 15 (210 mg, 0.34 mmol), Na₂CO₃ (36.5 mg, 0.34 mmol), EtOH (5 mL), toluene (10 mL), THF (1 mL), and water (5 mL). The reaction mixture was allowed to stir under a nitrogen atmosphere at 35° C. for 2 hours after which time the complete consumption of starting material was observed by TLC (80:20 v/v EtOAc/MeOH) and LC/MS (1.68 min (ES+) m/z (relative intensity) 1508.10 ([M+H]^(+.), 100)). The reaction mixture was diluted with EtOAc (100 mL) and washed with H₂O (1×100 mL), brine (200 mL), dried (MgSO₄), filtered and evaporated under reduced pressure to provide the crude product. Purification by flash chromatography (gradient elution: 100:0 v/v EtOAc/MeOH to 80:20 v/v EtOAc/MeOH) afforded the SEM protected dimer 24 (240 mg, 69%). ¹H NMR (400 MHz, CDCl₃) δ 8.42 (s, 1H), 7.76 (d, J=7.5 Hz, 2H), 7.63-7.49 (m, 4H), 7.45-7.28 (m, 9H), 7.25 (d, J=2.9 Hz, 1H), 6.87 (t, J=14.0 Hz, 2H), 6.41 (s, 1H), 5.63-5.49 (m, 2H), 5.25 (s, 1H), 4.71 (d, J=10.1 Hz, 2H), 4.68-4.57 (m, 2H), 4.49 (d, J=6.7 Hz, 2H), 4.20 (s, 1H), 4.16-4.02 (m, 4H), 4.00-3.87 (m, 7H), 3.86-3.61 (m, 7H), 3.30-3.21 (m, 4H), 3.19-3.05 (m, 2H), 2.69-2.54 (m, 4H), 2.37 (s, 3H), 2.04-1.92 (m, 4H), 1.91-1.79 (m, 4H), 1.72 (s, 2H), 1.46 (d, J=6.9 Hz, 3H), 1.04-0.82 (m, 8H), 0.04-−0.02 (m, 18H). MS (ES⁺) m/z (relative intensity) 1508.10 ([M+H]^(+.), 100).

(c) (9H-fluoren-9-yl)methyl ((S)-1-(((S)-1-((4-((S)-7-methoxy-8-((5-(((S)-7-methoxy-2-(4-(4-methylpiperazin-1-yl)phenyl)-5-oxo-5,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yl)oxy)pentyl)oxy)-5-oxo-5,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)amino)-3-methyl-1-oxobutan-2-yl)carbamate (25)

Super hydride (0.358 mL, 0.358 mmol, 1.0 M in THF) was added dropwise to a stirred solution of the SEM-tetralactam 24 (216 mg, 0.143 mmol) in anhydrous THF (10 mL) at -−78° C. The reaction mixture was allowed to stir for 3 hours after which time the complete conversion of starting material directly was observed by LC/MS (1.37 min (ES+) m/z (relative intensity) 608.15 (([M+2H]²⁺)/2, 100)). The reaction mixture was carefully diluted with H₂O (100 mL) and extracted with DCM (100 mL). The organic layers was washed with brine (100 mL), dried over MgSO₄, filtered and evaporated under reduced pressure to provide the intermediate SEM-carbinolamine. The white solids were immediately dissolved in MeOH (100 mL), DCM (10 mL) and H₂O (20 mL) and treated with flash silica gel (50 g). The thick suspension was allowed to stir at room temperature for 4 days after which time the formation of a significant quantity of desired product was observed by TLC (90:10 v/v CHCl₃/MeOH). The reaction mixture was filtered through a porosity 3 sinter funnel and the pad rinsed slowly and thoroughly with 90:10 v/v CHCl₃/MeOH until no further product eluted (checked by TLC). The filtrate was washed with brine (100 mL), dried (MgSO₄), filtered and evaporated in vacuo, followed by high vacuum drying, to provide the crude product. Purification by flash chromatography (gradient elution: HPLC grade 98:2 v/v CHCl₃/MeOH to 88:12 v/v CHCl₃/MeOH) gave 25 as a mixture of carbinolamine ethers and imine (80 mg, 46%). ¹H NMR (400 MHz, CDCl3) δ 8.52 (s, 1H), 7.87 (d, J=3.9 Hz, 2H), 7.75 (d, J=7.5 Hz, 2H), 7.66-7.26 (m, 12H), 6.90 (d, J=8.8 Hz, 2H), 6.81 (s, 1H), 6.64 (d, J=6.0 Hz, 1H), 5.37 (d, J=5.7 Hz, 1H), 4.74-4.58 (m, 2H), 4.54-4.31 (m, 4H), 4.26-3.98 (m, 6H), 3.94 (s, 2H), 3.86 (dd, J=13.6, 6.6 Hz, 1H), 3.63-3.48 (m, 2H), 3.37 (dd, J=16.5, 5.6 Hz, 2H), 3.31-3.17 (m, 4H), 2.66-2.51 (m, 4H), 2.36 (s, 3H), 2.16 (d, J=5.1 Hz, 1H), 2.06-1.88 (m, 4H), 1.78-1.55 (m, 6H), 1.46 (d, J=6.8 Hz, 3H), 0.94 (d, J=6.8 Hz, 6H). MS (ES⁺) m/z (relative intensity) 608.15 (([M+2H]²⁺)/2, 100).

(d) 1-(3-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)propanamido)-N—((S)-1-(((S)-1-((4-((S)-7-methoxy-8-((5-(((S)-7-methoxy-2-(4-(4-methylpiperazin-1-yl)phenyl)-5-oxo-5,11a-dihydro-1H -benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yl)oxy)pentyl)oxy)-5-oxo-5,11a-dihydro-1H -benzo[e]pyrrolo[1,2-a][1,4]diazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)amino)-3-methyl-1-oxobutan-2-yl)-3,6,9,12,15,18,21,24-octaoxaheptacosan-27-amide (26)

Piperidine (0.2 mL) was added to a solution of 25 (77 mg, 63.4 μmol) in DMF (1 mL). The reaction mixture was allowed to stir for 20 minutes. The reaction mixture was carefully diluted with DCM (50 mL) and washed with water (50 mL). The organic layers was washed with brine (100 mL), dried over MgSO₄, filtered and evaporated under reduced pressure to provide the unprotected valine intermediate. The crude residue was immediately redissolved in chloroform (5 mL). Mal(Peg)₈-acid (56 mg, 95 μmol) and EDCl (18 mg, 95 μmol) were added, followed by methanol (0.1 mL). The reaction was allowed to stir for 3 hours at room temperature at which point completion was observed by TLC and LC/MS (1.19 min (ES+) m/z (relative intensity) 784.25 (([M+2H]²⁺)/2, 100)). The reaction mixture was diluted with chloroform (50 mL), washed with water (100 mL), dried (MgSO₄), filtered and evaporated in vacuo, followed by high vacuum drying, to provide the crude product.

Purification by flash chromatography (gradient elution: HPLC grade 96:4 v/v CHCl₃/MeOH to 90:10 v/v CHCl₃/MeOH) gave 26 as a yellow solid (43 mg, 43%). ¹H NMR (400 MHz, CDCl₃) δ 8.73 (s, 1H), 7.88 (dd, J=7.6, 3.9 Hz, 2H), 7.75 (d, J=8.6 Hz, 2H), 7.52 (d, J=2.0 Hz, 2H), 7.44 (s, 1H), 7.40-7.28 (m, 4H), 6.91 (d, J=8.8 Hz, 2H), 6.81 (s, 2H), 6.69 (s, 2H), 6.48 (s, 1H), 4.72-4.63 (m, 1H), 4.46-4.34 (m, 2H), 4.25-4.03 (m, 6H), 3.95 (s, 4H), 3.84 (dd, J=17.2, 10.1 Hz, 4H), 3.72-3.46 (m, 30H), 3.44-3.32 (m, 4H), 3.30-3.20 (m, 4H), 2.75-2.63 (m, 1H), 2.59 (s, 4H), 2.55-2.43 (m, 3H), 2.37 (s, 3H), 2.29 (dd, J=12.7, 6.7 Hz, 1H), 2.03-1.89 (m, 4H), 1.72 (d, J=22.7 Hz, 8H), 1.46 (d, J=7.2 Hz, 3H), 1.01 (dd, J =11.5, 6.9 Hz, 6H). MS (ES⁺) m/z (relative intensity) 784.25 (([M+2H]²⁺)/2, 100).

Variations in General Experimental Methods for Example 4

The general methods for Example 4 are the same as above, except for:

Mass spectroscopy (MS) data were collected using a Waters Micromass LCT instrument coupled to a Waters 2795 HPLC separations module. Thin Layer Chromatography (TLC) was performed on silica gel aluminium plates (Merck 60, F₂₅₄). All other chemicals and solvents were used as supplied without further purification.

LCMS data were obtained using a Shimadzu Nexera series LC/MS with a Shimadzu LCMS-2020 quadrupole MS, with Electrospray ionisation. Mobile phase A—0.1% formic acid in water. Mobile phase B—0.1% formic acid in acetonitrile. Flow rate of 0.80 ml/min. Gradient from 5% B rising up to 100% B over 2.00 min, remaining at 100% B for 0.50 min and then back down to 5% B over 0.05 min (held for 0.45 min). The total run time is 3 min. Column: Waters Aquity UPLC BEH Shield RP18 1.7 μm, 2.1×50 mm.

Example 4 (i) (S)-((pentane-1,5-diylbis(oxy))bis(2-amino-5-methoxy-4,1-phenylene))bis(((S)-2-(((tert -butyldimethylsilyl)oxy)methyl)-4-methyl-2,3-dihydro-1H-pyrrol-1-yl)methanone) (35)

(a) (S,R)-((pentane-1,5-diylbis(oxy))bis(5-methoxy-2-nitro-4,1-phenylene))bis(((2S,4R)-2-(((tert-butyldimethylsilyl)oxy)methyl)-4-hydroxypyrrolidin-1-yl) methanone) (31)

Anhydrous DMF (approx. 0.5 mL) was added dropwise to a stirred suspension of 4,4′-(pentane-1,5-diylbis(oxy))bis(5-methoxy-2-nitrobenzoic acid) (29) (36.64 g, 74.0 mmol) and oxalyl chloride (18.79 mL, 0.222 mol, 3.0 eq.) in anhydrous DCM (450 mL) until vigorous effervescence occurred and the reaction mixture was left to stir overnight. The reaction mixture was evaporated to dryness, and triturated with diethyl ether. The resulting yellow precipitate was filtered from solution, washed with diethyl ether (100 mL) and immediately added to a solution of (3R,5S)-5-((tert-butyldimethylsilyloxy)methyl) pyrrolidin-3-ol (30) (39.40 g, 0.170 mol, 2.3 eq.) and anhydrous triethylamine (82.63 mL, 0.592 mol, 8 eq.) in anhydrous DCM (400 mL) at −40° C. The reaction mixture was allowed to slowly warm to room temperature (over 2.5 hours) after which, LCMS analysis indicated complete reaction. DCM (250 mL) was added and the mixture was transferred into a separating funnel. The organic layer was washed successively with 0.1M HCl (2×800 mL), saturated NaHCO₃ (500 mL) and brine (300 mL). After drying over MgSO₄ and filtration, evaporation of the solvent left the product as a yellow foam (62.8 g, 92%). LC/MS: RT 1.96 min; MS (ES+) m/z (relative intensity) 921.45 ([M+H]⁺, 100).

(b) (5S,5′S)-1,1′-(4,4′-(pentane-1,5-diylbis(oxy))bis(5-methoxy-2-nitrobenzoyl))bis(5-(((tert -butyldimethylsilyl)oxy)methyl)pyrrolidin-3-one) (32)

Trichloroisocyanuric acid (21.86 g, 94.07 mmol, 1.4 eq) was added in one portion to a solution of diol 31 (61.90 g, 67.20 mmol) and TEMPO (2.10 g, 13.44 mmol, 0.2 eq) in anhydrous DCM (500 mL) under an atmosphere of argon at 0° C. The reaction mixture was stirred at 0° C. for 20 minutes after which, LCMS analysis of the reaction mixture showed complete reaction. The reaction mixture was diluted with DCM (400 mL) and washed with saturated sodium bicarbonate (500 mL), 0.2 M sodium thiosulfate solution (600 mL), brine (400 mL) and dried (MgSO₄). Evaporation of the solvent gave the crude product. Flash chromatography [gradient elution 80% n-hexane/20% ethyl acetate to 100% ethyl acetate] gave pure 31 as yellow solid (49.30 g, 80%). LC/MS: RT 2.03 min; MS (ES+) m/z (relative intensity) 917.55 ([M+H]⁺, 100).

(c) (5S,5′S)-1,1′-(4,4′-(pentane-1, 5-diylbis(oxy))bis(5-methoxy-2-nitrobenzoyl))bis(5-(((tert -butyldimethylsilyl)oxy)methyl)-4,5-dihydro-1H-pyrrole-3,1-diyl)bis(trifluoromethanesulfonate), (33)

Triflic anhydride (24.19 mL, 0.144 mol, 6.0 eq) was added dropwise to a vigorously stirred solution of bis-ketone 31 (21.98 g, 23.96 mmol) in anhydrous DCM (400 mL) containing 2,6-lutidine (22.33 mL, 0.192 mol, 8.0 eq) at −40° C. The reaction mixture was stirred at −40° C. for 30 min after which, LCMS analysis indicated complete reaction. Reaction mixture was rapidly diluted with DCM (500 mL) and washed with ice-cold water (600 mL), ice-cold saturated sodium bicarbonate (400 mL) and brine (500 mL), dried over MgSO₄, filtered and evaporated to leave a crude brown oil. Flash chromatography [gradient elution 80% n-hexane/20% ethyl acetate to 66% n-hexane/33% ethyl acetate] gave pure 33 as a brown foam (16.40 g, 58%). LC/MS: RT 2.28 min; MS (ES+m/z (relative intensity) no data.

(d) (S)-((pentane-1,5-diylbis(oxy))bis(5-methoxy-2-nitro-4,1-phenylene))bis(((S)-2-(((tert -butyldimethylsilyl)oxy)methyl)-4-methyl-2,3-dihydro-1H-pyrrol-1-yl)methanone) (34)

Triflate 33 (5.06 g, 4.29 mmol), methyl boronic acid (1.80 g, 30.00 mmol, 7 eq) and triphenylarsine (1.05 g, 3.43 mmol, 0.8 eq) were dissolved in anhydrous dioxane and stirred under argon. Pd (II) bisbenzonitrile chloride was then added and the reaction mixture heated rapidly to 80° C. for 20 min. Reaction mixture cooled, filtered through Celite (washed through with ethyl acetate), filtrate washed with water (500 mL), brine (500 mL), dried over MgSO₄, filtered and evaporated. Flash chromatography [gradient elution 50% n-hexane/50% ethyl acetate] gave pure 34 as a brown foam (4.31 g, 59%). LC/MS: RT 2.23 min; MS (ES+) m/z (relative intensity) 913.50 ([M+H]⁺, 100).

(e) (S)-((pentane-1,5-diylbis(oxy))bis(2-amino-5-methoxy-4,1-phenylene))bis(((S)-2-(((tert -butyldimethylsilyl)oxy)methyl)-4-methyl-2,3-dihydro-1H-pyrrol-1-yl)methanone) (35)

Zinc dust (26.48 g, 0.405 mol, 36.0 eq) was added in one portion to a solution of bis-nitro compound 34 (10.26 g, 11.24 mmol) in 5% formic acid/methanol (200 mL) keeping the temperature between 25-30° C. with the aid of a cold water bath. The reaction was stirred at 30° C. for 20 minutes after which, LCMS showed complete reaction. The reaction mixture was filtered through Celite to remove the excess zinc, which was washed with ethyl acetate (600 mL). The organic fractions were washed with water (500 mL), saturated sodium bicarbonate (500 mL) and brine (400 mL), dried over MgSO₄ and evaporated. Flash chromatography [gradient elution 100% chloroform to 99% chloroform/1% methanol] gave pure 35 as an orange foam (6.22 g, 65%). LC/MS: RT 2.20 min; MS (ES+) m/z (relative intensity) 853.50 ([M+H]⁺, 100).

(ii) 4-((R)-2-((R)-2-(((allyloxy)carbonyl)amino)-3-methylbutanamido)propanamido)benzyl 4-((10R,13R)-10-isopropyl-13-methyl-8,11-dioxo-2,5-dioxa-9,12-diazatetradecanamido)benzyl ((S)-(pentane-1,5-diylbis(oxy))bis(2-((S)-2-(hydroxymethyl)-4-methyl-2,3-dihydro-1H-pyrrole-1-carbonyl)-4-methoxy-5,1-phenylene))dicarbamate (40)

(a) Allyl (5-((5-(5-amino-4-((S)-2-(((tert-butydimethysily)oxy)methyl)-4-methy-2,3-dihydro-1H-pyrrole-1-carbonyl)-2-methoxyphenoxy)pentyl)oxy)-2-((S)-2-(((tert -butyldimethylsilyl)oxy)methyl)-4-methyl-2,3-dihydro-1H-pyrrole-1-carbonyl)-4-methoxyphenyl)carbamate (36)

Pyridine (1.156 mL, 14.30 mmol, 1.5 eq) was added to a solution of the bis-aniline 35 (8.14 g, 9.54 mmol) in anhydrous DCM (350 mL) at −78° C. under an atmosphere of argon. After 5 minutes, allyl chloroformate (0.911 mL, 8.58 mmol, 0.9 eq) was added and the reaction mixture allowed to warm to room temperature. The reaction mixture was diluted with DCM (250 mL), washed with saturated CuSO₄ solution (400 mL), saturated sodium bicarbonate (400 mL) and brine (400 mL), dried over MgSO₄. Flash chromatography [gradient elution 66% n-hexane/33% ethyl acetate to 33% n-hexane/66% ethyl acetate] gave pure 36 as an orange foam (3.88 g, 43%). LC/MS: RT 2.27 min; MS (ES+) m/z (relative intensity) 937.55 ([M+H]⁺, 100).

(b) Allyl 4-((10S,13S)-10-isopropyl-13-methyl-8,11-dioxo-2,5-dioxa-9,12-diazatetradecanamido)benzyl((S)-(pentane-1, 5-diylbis(oxy))bis(2-((S)-2-(((tert -butyldimethylsilyl)oxy)methyl)-4-methyl-2,3-dihydro-1H-pyrrole-1-carbonyl)-4-methoxy-5,1-phenylene))dicarbamate (37)

Triethylamine (0.854 mL, 6.14 mmol, 2.2 eq) was added to a stirred solution of the aniline 36 (2.62 g, 2.79 mmol) and triphosgene (0.30 g, 1.00 mmol, 0.36 eq) in anhydrous THF (50 mL) under argon 0° C. The reaction mixture was stirred at room temperature for 5 minutes. LCMS analysis of an aliquot quenched with methanol, showed formation of the isocyanate. A solution of mPEG₂-Val-Ala-PAB-OH (1.54 g, 3.63 mmol, 1.3 eq) and triethylamine (0.583 mL, 4.19 mmol, 1.5 eq) in dry THF (50 mL) was added in one portion and the resulting mixture was stirred overnight at 40° C. The solvent of the reaction mixture was evaporated leaving a crude product. Flash chromatography [gradient elution 100% chloroform to 98% chloroform/2% methanol] gave pure 37 as a light orange solid (2.38 g, 62%). LC/MS: RT 2.29 min; MS (ES+) m/z (relative intensity) no data.

(c) 4-((10S,13S)-10-isopropyl-13-methyl-8,11-dioxo-2,5-dioxa-9,12-diazatetradecanamido)benzyl (5-((5-(5-amino-4-((S)-2-(((tert-butyldimethylsilyl)oxy)methyl)-4-methyl-2,3-dihydro-1H-pyrrole-1-carbonyl)-2-methoxyphenoxy)pentyl)oxy)-2-((S)-2-(((tert -butyldimethylsilyl)oxy)methyl)-4-methyl-2,3-dihydro-1H-pyrrole-1-carbonyl)-4-methoxyphenyl)carbamate (38)

Tetrakis(triphenylphosphine)palladium (39 mg, 0.034 mmol, 0.02 eq) was added to a stirred solution of 37 (2.35 g, 1.69 mmol) and pyrrolidine (0.35 mL, 4.24 mmol, 2.5 eq) in anhydrous DCM (25 mL) under argon at room temperature. Reaction mixture allowed to stir for 45 min then diluted with DCM (100 mL), washed with saturated ammonium chloride solution (100 mL), brine (100 mL), dried over MgSO₄, filtered and evaporated. Flash chromatography [gradient elution 100% chloroform to 95% chloroform/5% methanol] gave pure 38 as a yellow solid (1.81 g, 82%). LC/MS: RT 2.21 min; MS (ES+) m/z (relative intensity) 1303.65 ([M+H]⁺, 100).

(d) 4-((R)-2-((R)-2-(((allyloxy)carbonyl)amino)-3-methylbutanamido)propanamido)benzyl 4-((10R,13R)-10-isopropyl-13-methyl-8,11-dioxo-2,5-dioxa-9,12-diazatetradecanamido)benzyl ((S)-(pentane-1,5-diylbis(oxy))bis(2-((S)-2-(((tert-butydimethysily)oxy)methy)-4-methy-2,3-dihydro-1H-pyrrole-1-carbonyl)-4-methoxy-5,1-phenylene))dicarbamate (39)

Triethylamine (0.419 mL, 3.01 mmol, 2.2 eq) was added to a stirred solution of the aniline 38 (1.78 g, 1.37 mmol) and triphosgene (0.15 g, 0.49 mmol, 0.36 eq) in anhydrous THF (50 mL) under argon 0° C. The reaction mixture was stirred at room temperature for 5 min. LCMS analysis of an aliquot quenched with methanol, showed formation of the isocyanate. A solution of Alloc-Val-Ala-PAB-OH (0.67 g, 1.78 mmol, 1.3 eq) and triethylamine (0.29 mL, 2.05 mmol, 1.5 eq) in dry THF (45 mL) was added in one portion and the resulting mixture was stirred overnight at 40° C. The solvent of the reaction mixture was evaporated leaving a crude product. Flash chromatography [gradient elution 100% ethyl acetate to 97% ethyl acetate/3% methanol] gave pure 39 as a pale yellow solid (1.33 g, 57%). LC/MS: RT 2.21 min; MS (ES+) m/z (relative intensity) no data.

(e) 4-((R)-2-((R)-2-(((allyloxy)carbonyl)amino)-3-methylbutanamido)propanamido)benzyl 4-((10R,13R)-10-isopropyl-13-methyl-8,11-dioxo-2,5-dioxa-9,12-diazatetradecanamido)benzyl ((S)-(pentane-1,5-diylbis(oxy))bis(2-((S)-2-(hydroxymethyl)-4-methyl-2,3-dihydro-1H-pyrrole-1-carbonyl)-4-methoxy-5,1-phenylene))dicarbamate (40)

Tetra-n-butylammonium fluoride (1 M, 1.52 mL, 1.52 mmol, 2.0 eq) was added to a solution of the TBS protected compound 39 (1.30 g, 0.76 mmol) in anhydrous THF (15 mL). The reaction mixture was stirred at room temperature for 4 hours. The reaction mixture was diluted with chloroform (100 mL) and washed sequentially with water (40 mL) and brine (40 mL). The organic phase was dried over MgSO₄ and evaporated to leave a yellow solid. Flash chromatography [gradient elution 95% ethyl acetate/5% methanol to 90% ethyl acetate/10% methanol] gave pure 40 as a pale yellow solid (1.00 g, 89%). LC/MS: RT 1.60 min; MS (ES+) m/z (relative intensity) 1478.45 (100).

(iii) (11S,11aS)-4-((2R,5R)-37-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)-5-isopropyl-2-methyl-4,7,35-trioxo-10,13,16,19,22,25,28,31-octaoxa-3,6,34-triazaheptatriacontanamido)benzyl 11-hydroxy-8-((5-(((11S,11aS)-11-hydroxy-10-(((4-((10R,13R)-10-isopropyl-13-methyl-8,11-dioxo-2,5-dioxa-9,12-diazatetradecanamido)benzyl)oxy)carbonyl)-7-methoxy-2-methyl-5-oxo-5,10,11,11a-tetrahydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-8-yl)oxy)pentyl)oxy)-7-methoxy-2-methyl-5-oxo-1,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepine-10(5H) -carboxylate (43)

(a) (11S,11aS)-4-((R)-2-((R)-2-(((allyloxy)carbonyl)amino)-3-methylbutanamido)propanamido)benzyl 11-hydroxy-8-((5-(((11S,11aS)-11-hydroxy-10-(((4-((10R,13R)-10-isopropyl-1,3-methyl-8,11-dioxo-2,5-dioxa-9, 12-diazatetradecanamido)benzyl)oxy)carbonyl)-7-methoxy-2-methyl-5-oxo-5,10,11,11a -tetrahydro-1H-pyrrolo[2, 1-c][1,4]benzodiazepin-8-yl)oxy)pentyl) oxy)-7-methoxy-2-methyl-5-oxo-11,11a-dihydro-1H-pyrrolo[2, 1-c][1,4]benzodiazepine-10 (5H)-carboxylate (41)

Dess-Martin periodinane (0.59 g, 1.38 mmol, 2.1 eq) was added to a stirred solution of 40 (0.97 g, 0.66 mmol) in anhydrous DCM under argon at room temperature. The reaction mixture was allowed to stir for 4 hours. Reaction mixture diluted with DCM (100 mL), washed with saturated sodium bicarbonate solution (3×100 mL), water (100 mL), brine (100 mL), dried over MgSO₄, filtered and evaporated. Flash chromatography [gradient elution 100% chloroform to 95% chloroform/5% methanol] gave pure 41 as a pale yellow solid (0.88 g, 90%). LC/MS: RT 1.57 min; MS (ES+) m/z (relative intensity) 1473.35 (100).

(b) (11S,11aS)-4-((R)-2-((R)-2-amino-3-methylbutanamido)propanamido)benzyl 11-hydroxy-8-((5-(((11S,11aS)-11-hydroxy-10-((4-((((10R,13R)-10-isopropyl-13-methyl-8,11-dioxo-2,5-dioxa-9,12-diazatetradecanamido)benzyl)oxy)carbonyl)-7-methoxy-2-methyl-5-oxo-5,10,11,11a-tetrahydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-8-yl)oxy)pentyl)oxy)-7-methoxy-2-methyl-5-oxo-11,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepine-10(5H)-carboxylate (42)

Tetrakis(triphenylphosphine)palladium (5 mg, 0.004 mmol, 0.06 eq) was added to a solution of 41 (105 mg, 0.071 mmol) and pyrrolidine (7 μL, 0.086 mmol, 1.2 eq) in anhydrous DCM (5 mL). The reaction mixture was stirred 15 minutes then diluted with chloroform (50 mL) and washed sequentially with saturated aqueous ammonium chloride (30 mL) and brine (30 mL). The organic phase was dried over magnesium sulphate, filtered and evaporated. Flash chromatography [gradient elution 100% chloroform to 90% chloroform/10% methanol] gave pure 42 as a pale yellow solid (54 mg, 55%). LC/MS: RT 1.21 min; MS (ES+) m/z (relative intensity) 1389.50 (100).

(c) (11S,11aS)-4-((2R,5R)-37-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)-5-isopropyl-2-methyl-4,7,35-trioxo-10,13,16,19,22,25,28,31-octaoxa-3,6,34-triazaheptatriacontanamido)benzyl 11-hydroxy-8-((5-(((11S,11aS)-11-hydroxy-10-(((4-((((10R,13R)-10-isopropyl-13-methyl-8,11-dioxo-2,5-dioxa-9,12-diazatetradecanamido)benzyl)oxy)carbonyl)-7-methoxy-2-methyl-5-oxo-5,10,11,11a-tetrahydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-8-yl)oxy)pentyl)oxy)-7-methoxy-2-methyl-5-oxo-11,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepine-10(5H) -carboxylate (43)

N-(3-Dimethylaminopropyl)-N′-ethylcarbodiimide (28 mg, 0.146 mmol, 1 eq) was added to a solution of 42 (203 mg, 0.146 mmol) and maleimide-PEG₈ acid (87 mg, 0.146 mmol) in chloroform (5 mL). The reaction was stirred for 1.5 h then diluted with chloroform (50 mL), washed with water (50 mL), brine (30 mL), dried over magnesium sulphate, filtered and evaporated. Flash chromatography [gradient elution 100% DCM to 90% DCM/10% methanol] gave 43 as a pale yellow solid (205 mg, 72%). LC/MS: RT 5.75 min; MS (ES+) m/z (relative intensity) 982.90 (100), 1963.70 (5).

General Experimental Methods for Example 5

Optical rotations were measured on an ADP 220 polarimeter (Bellingham Stanley Ltd.) and concentrations (c) are given in g/100 mL. Melting points were measured using a digital melting point apparatus (Electrothermal). IR spectra were recorded on a Perkin-Elmer Spectrum 1000 FT IR Spectrometer. ¹H and ¹³C NMR spectra were acquired at 300 K using a Bruker Avance NMR spectrometer at 400 and 100 MHz, respectively. Chemical shifts are reported relative to TMS (δ=0.0 ppm), and signals are designated as s (singlet), d (doublet), t (triplet), dt (double triplet), dd (doublet of doublets), ddd (double doublet of doublets) or m (multiplet), with coupling constants given in Hertz (Hz). Mass spectroscopy (MS) data were collected using a Waters Micromass ZQ instrument coupled to a Waters 2695 HPLC with a Waters 2996 PDA. Waters Micromass ZQ parameters used were: Capillary (kV), 3.38; Cone (V), 35; Extractor (V), 3.0; Source temperature (° C.), 100; Desolvation Temperature (° C.), 200; Cone flow rate (L/h), 50; De-solvation flow rate (L/h), 250. High-resolution mass spectroscopy (HRMS) data were recorded on a Waters Micromass QTOF Global in positive W-mode using metal-coated borosilicate glass tips to introduce the samples into the instrument. Thin Layer Chromatography (TLC) was performed on silica gel aluminium plates (Merck 60, F₂₅₄), and flash chromatography utilised silica gel (Merck 60, 230-400 mesh ASTM). Except for the HOBt (NovaBiochem) and solid-supported reagents (Argonaut), all other chemicals and solvents were purchased from Sigma-Aldrich and were used as supplied without further purification. Anhydrous solvents were prepared by distillation under a dry nitrogen atmosphere in the presence of an appropriate drying agent, and were stored over 4 Å molecular sieves or sodium wire. Petroleum ether refers to the fraction boiling at 40-60° C.

General LC/MS conditions: The HPLC (Waters Alliance 2695) was run using a mobile phase of water (A) (formic acid 0.1%) and acetonitrile (B) (formic acid 0.1%). Gradient: initial composition 5% B over 1.0 min then 5% B to 95% B over 2.5 min. The composition was held for 0.5 min at 95% B, and then returned to 5% B in 0.1 minutes and held there for 0.9 min. Total gradient run time equals 5 min. Flow rate 3.0 mL/min, 400 μL was split via a zero dead volume tee piece which passes into the mass spectrometer. Wavelength detection range: 220 to 400 nm. Function type: diode array (535 scans). Column: Phenomenex® Onyx Monolithic C18 50×4.60 mm

Example 5 (i) (S)-(2-amino-5-methoxy-4-((triisopropylsilyl)oxy)phenyl)(2-(((tert -butyldimethylsilyl)oxy)methyl)-4-methyl-2,3-dihydro-1H-pyrrol-1-yl)methanone (59)

(a) 5-methoxy-2-nitro-4-((triisopropylsilyl)oxy)benzaldehyde (52)

Neat triisopropylsilylchloride (56.4 mL, 262 mmol) was added to a mixture of imidazole (48.7 g, 715.23 mmol) and 4-hydroxy-5-methoxy-2-nitrobenzaldehyde 51 (47 g, 238 mmol) (ground together). The mixture was heated until the phenol and imidazole melted and went into solution (100° C.). The reaction mixture was allowed to stir for 15 minutes and was then allowed to cool, whereupon a solid was observed to form at the bottom of the flask (imidazole chloride). The reaction mixture was diluted with 5% EtOAc/hexanes and loaded directly onto silica gel and the pad was eluted with 5% EtOAc/hexanes, followed by 10% EtOAc/hexanes (due to the low excess, very little unreacted TIPSCI was found in the product). The desired product was eluted with 5% ethyl acetate in hexane. Excess eluent was removed by rotary evaporation under reduced pressure, followed by drying under high vacuum to afford a crystalline light sensitive solid (74.4 g, 88%). Purity satisfactory by LC/MS (4.22 min (ES+) m/z (relative intensity) 353.88 ([M+H]^(+.), 100)); ¹H NMR (400 MHz, CDCl₃) δ 10.43 (s, 1H), 7.60 (s, 1H), 7.40 (s, 1H), 3.96 (s, 3H), 1.35-1.24 (m, 3H), 1.10 (m, 18H).

(b) 5-methoxy-2-nitro-4-((triisopropylsilyl)oxy)benzoic acid (53)

A solution of sodium chlorite (47.3 g, 523 mmol, 80% technical grade) and sodium dihydrogenphosphate monobasic (35.2 g, 293 mmol) (NaH₂PO₄) in water (800 mL) was added to a solution of compound 52 (74 g, 209 mmol) in tetrahydrofuran (500 mL) at room temperature. Hydrogen peroxide (60% w/w, 140 mL, 2.93 mol) was immediately added to the vigorously stirred biphasic mixture. The reaction mixture evolved gas (oxygen), the starting material dissolved and the temperature of the reaction mixture rose to 45° C. After 30 minutes LC/MS revealed that the reaction was complete. The reaction mixture was cooled in an ice bath and hydrochloric acid (1 M) was added to lower the pH to 3 (this step was found unnecessary in many instances, as the pH at the end of the reaction is already acidic; please check the pH before extraction). The reaction mixture was then extracted with ethyl acetate (1 L) and the organic phases washed with brine (2×100 mL) and dried over magnesium sulphate. The organic phase was filtered and excess solvent removed by rotary evaporation under reduced pressure to afford the product 53 in quantitative yield as a yellow solid. LC/MS (3.93 min (ES−) m/z (relative intensity) 367.74 ([M−H]^(−.), 100)); ¹H NMR (400 MHz, CDCl₃) δ 7.36 (s, 1H), 7.24 (s, 1H), 3.93 (s, 3H), 1.34-1.22 (m, 3H), 1.10 (m, 18H).

(c) ((2S,4R)-2-(((tert-butyldimethylsilyl)oxy)methyl)-4-hydroxypyrrolidin-1-yl) (5-methoxy-2-nitro-4-((triisopropylsilyl)oxy)phenyl)methanone (55)

DCC (29.2 g, 141 mmol, 1.2 eq) was added to a solution of acid 53 (43.5 g, 117.8 mmol, 1 eq), and hydroxybenzotriazole hydrate (19.8 g, 129.6 mmol, 1.1 eq) in dichloromethane (200 mL) at 0° C. The cold bath was removed and the reaction was allowed to proceed for 30 mins at room temperature, at which time a solution of (2S,4R)-2-t -butyldimethylsilyloxymethyl-4-hydroxypyrrolidine 54 (30 g, 129.6 mmol, 1.1 eq) and triethylamine (24.66 mL, 176 mmol, 1.5 eq) in dichloromethane (100 mL) was added rapidly at −10° C. under argon (on large scale, the addition time could be shortened by cooling the reaction mixture even further. The reaction mixture was allowed to stir at room temperature for 40 minutes to 1 hour and monitored by LC/MS and TLC (EtOAc). The solids were removed by filtration over celite and the organic phase was washed with cold aqueous 0.1 M HCl until the pH was measured at 4 or 5. The organic phase was then washed with water, followed by saturated aqueous sodium bicarbonate and brine. The organic layer was dried over magnesium sulphate, filtered and excess solvent removed by rotary evaporation under reduced pressure. The residue was subjected to column flash chromatography (silica gel; gradient 40/60 ethyl acetate/hexane to 80/20 ethyl acetate/hexane). Excess solvent was removed by rotary evaporation under reduced pressure afforded the pure product 55, (45.5 g of pure product 66%, and 17 g of slightly impure product, 90% in total). LC/MS 4.43 min (ES+) m/z (relative intensity) 582.92 ([M+H]^(+.), 100); ¹H NMR (400 MHz, CDCl₃) δ 7.66 (s, 1H), 6.74 (s, 1H), 4.54 (s, 1H), 4.40 (s, 1H), 4.13 (s, 1H), 3.86 (s, 3H), 3.77 (d, J=9.2 Hz, 1H), 3.36 (dd, J=11.3, 4.5 Hz, 1H), 3.14-3.02 (m, 1H), 2.38-2.28 (m, 1H), 2.10 (ddd, J=13.3, 8.4, 2.2 Hz, 1H), 1.36-1.19 (m, 3H), 1.15-1.05 (m, 18H), 0.91 (s, 9H), 0.17-0.05 (m, 6H), (presence of rotamers).

(d) (S)-5-(((tert-butyldimethylsilyl)oxy)methyl)-1-(5-methoxy-2-nitro-4-((triisopropylsilyl)oxy)benzoyl)pyrrolidin-3-one (56)

TCCA (8.82 g, 40 mmol, 0.7 eq) was added to a stirred solution of 55 (31.7 g, 54 mmol, 1 eq) and TEMPO (0.85 g, 5.4 mmol, 0.1 eq) in dry dichloromethane (250 mL) at 0° C. The reaction mixture was vigorously stirred for 20 minutess, at which point TLC (50/50 ethyl acetate/hexane) revealed complete consumption of the starting material. The reaction mixture was filtered through celite and the filtrate washed with aqueous saturated sodium bicarbonate (100 mL), sodium thiosulphate (9 g in 300 mL), brine (100 mL) and dried over magnesium sulphate. Rotary evaporation under reduced pressure afforded product 6 in quantitative yield. LC/MS 4.52 min (ES+) m/z (relative intensity) 581.08 ([M+H]^(+.), 100); ¹H NMR (400 MHz, CDCl₃) δ 7.78-7.60 (m, 1H), 6.85-6.62 (m, 1H), 4.94 (dd, J=30.8, 7.8 Hz, 1H), 4.50-4.16 (m, 1H), 3.99-3.82 (m, 3H), 3.80-3.34 (m, 3H), 2.92-2.17 (m, 2H), 1.40-1.18 (m, 3H), 1.11 (t, J=6.2 Hz, 18H), 0.97-0.75 (m, 9H), 0.15-−0.06 (m, 6H), (presence of rotamers).

(e) (S)-5-(((tert-butyldimethylsilyl)oxy)methyl)-1-(5-methoxy-2-nitro-4-((triisopropylsilyl)oxy)benzoyl)-4, 5-dihydro-1H-pyrrol-3-yl trifluoromethanesulfonate (57)

Triflic anhydride (27.7 mL, 46.4 g, 165 mmol, 3 eq) was injected (temperature controlled) to a vigorously stirred suspension of ketone 56 (31.9 g, 55 mmol, 1 eq) in dry dichloromethane (900 mL) in the presence of 2,6-lutidine (25.6 mL, 23.5 g, 220 mmol, 4 eq, dried over sieves) at −50° C. (acetone/dry ice bath). The reaction mixture was allowed to stir for 1.5 hours when LC/MS, following a mini work-up (water/dichloromethane), revealed the reaction to be complete. Water was added to the still cold reaction mixture and the organic layer was separated and washed with saturated sodium bicarbonate, brine and magnesium sulphate. The organic phase was filtered and excess solvent was removed by rotary evaporation under reduced pressure. The residue was subjected to column flash chromatography (silica gel; 10/90 v/v ethyl acetate/hexane), removal of excess eluent afforded the product 57 (37.6 g, 96%) LC/MS, method 2, 4.32 min (ES+) m/z (relative intensity) 712.89 ([M+H]^(+.), 100); ¹H NMR (400 MHz, CDCl₃) δ 7.71 (s, 1H), 6.75 (s, 1H), 6.05 (d, J=1.8 Hz, 1H), 4.78 (dd, J=9.8, 5.5 Hz, 1H), 4.15-3.75 (m, 5H), 3.17 (ddd, J=16.2, 10.4, 2.3 Hz, 1H), 2.99 (ddd, J=16.3, 4.0, 1.6 Hz, 1H), 1.45-1.19 (m, 3H), 1.15-1.08 (m, 18H), 1.05 (s, 6H), 0.95-0.87 (m, 9H), 0.15-0.08 (m, 6H).

(f) (S)-(2-(((tert-butyldimethylsilyl)oxy)methyl)-4-methyl-2,3-dihydro-1H-pyrrol-1-yl) (5-methoxy-2-nitro-4-((triisopropylsilyl)oxy)phenyl)methanone (58)

Triphenylarsine (1.71 g, 5.60 mmol, 0.4 eq) was added to a mixture of triflate 57 (10.00 g, 14 mmol, 1 eq), methylboronic acid (2.94 g, 49.1 mmol, 3.5 eq), silver oxide (13 g, 56 mmol, 4 eq) and potassium phosphate tribasic (17.8 g, 84 mmol, 6 eq) in dry dioxane (80 mL) under an argon atmosphere. The reaction was flushed with argon 3 times and bis(benzonitrile)palladium(II) chloride (540 mg, 1.40 mmol, 0.1 eq) was added. The reaction was flushed with argon 3 more times before being warmed instantaneously to 110° C. (the drysyn heating block was previously warmed to 110° C. prior addition of the flask). After 10 mins the reaction was cooled to room temperature and filtered through a pad celite. The solvent was removed by rotary evaporation under reduced pressure. The resulting residue was subjected to column flash chromatography (silica gel; 10% ethyl acetate/hexane). Pure fractions were collected and combined, and excess eluent was removed by rotary evaporation under reduced pressure afforded the product 58 (4.5 g, 55%). LC/MS, 4.27 min (ES+) m/z (relative intensity) 579.18 ([M+H]^(+.), 100); ¹H NMR (400 MHz, CDCl₃) δ 7.70 (s, 1H), 6.77 (s, 1H), 5.51 (d, J=1.7 Hz, 1H), 4.77-4.59 (m, 1H), 3.89 (s, 3H), 2.92-2.65 (m, 1H), 2.55 (d, J=14.8 Hz, 1H), 1.62 (d, J=1.1 Hz, 3H), 1.40-1.18 (m, 3H), 1.11 (s, 9H), 1.10 (s, 9H), 0.90 (s, 9H), 0.11 (d, J=2.3 Hz, 6H).

(g) (S)-(2-amino-5-methoxy-4-((triisopropylsilyl)oxy)phenyl) (2-(((tert -butyldimethylsilyl)oxy)methyl)-4-methyl-2,3-dihydro-1H-pyrrol-1-yl)methanone (59)

Zinc powder (28 g, 430 mmol, 37 eq) was added to a solution of compound 58 (6.7 g, 11.58 mmol) in 5% formic acid in ethanol v/v (70 mL) at around 15° C. The resulting exotherm was controlled using an ice bath to maintain the temperature of the reaction mixture below 30° C. After 30 minutes the reaction mixture was filtered through a pad of celite. The filtrate was diluted with ethyl acetate and the organic phase was washed with water, saturated aqueous sodium bicarbonate and brine. The organic phase was dried over magnesium sulphate, filtered and excess solvent removed by rotary evaporation under reduced pressure. The resulting residue was subjected to flash column chromatography (silica gel; 10% ethyl acetate in hexane). The pure fractions were collected and combined and excess solvent was removed by rotary evaporation under reduced pressure to afford the product 59 (5.1 g, 80%). LC/MS, 4.23 min (ES+) m/z (relative intensity) 550.21 ([M+H]^(+.), 100); ¹H NMR (400 MHz, CDCl₃) δ 7.28 (s, 1H), 6.67 (s, 1H), 6.19 (s, 1H), 4.64-4.53 (m, J=4.1 Hz, 1H), 4.17 (s, 1H), 3.87 (s, 1H), 3.77-3.69 (m, 1H), 3.66 (s, 3H), 2.71-2.60 (m, 1H), 2.53-2.43 (m, 1H), 2.04-1.97 (m, J=11.9 Hz, 1H), 1.62 (s, 3H), 1.26-1.13 (m, 3H), 1.08-0.99 (m, 18H), 0.82 (s, 9H), 0.03-−0.03 (m, J=6.2 Hz, 6H).

(ii) (11S,11aS)-allyl 11-((tert-butyldimethylsilyl)oxy)-8-((5-iodopentyl)oxy)-7-methoxy-2-methyl-5-oxo-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate

(a) (S)-allyl (2-(2-(((tert-butyldimethylsilyl)oxy)methyl)-4-methyl-2,3-dihydro-1H-pyrrole-1-carbonyl)-4-methoxy-5-((triisopropylsilyl)oxy)phenyl)carbamate (60)

Allyl chloroformate (0.30 mL, 3.00 mmol, 1.1 eq) was added to a solution of amine 59 (1.5 g, 2.73 mmol) in the presence of dry pyridine (0.48 mL, 6.00 mmol, 2.2 eq) in dry dichloromethane (20 mL) at −78° C. (acetone/dry ice bath). After 30 minutes, the bath was removed and the reaction mixture was allowed to warm to room temperature. The reaction mixture was diluted with dichloromethane and saturated aqueous copper sulphate was added. The organic layer was then washed sequentially with saturated aqueous sodium bicarbonate and brine. The organic phase was dried over magnesium sulphate, filtered and excess solvent removed by rotary evaporation under reduced pressure to afford the product 60 which was used directly in the next reaction. LC/MS, 4.45 min (ES+) m/z (relative intensity) 632.91 ([M+H]^(+.), 100)

(b) (S)-allyl (2-(2-(hydroxymethyl)-4-methyl-2,3-dihydro-1H-pyrrole-1-carbonyl)-4-methoxy-5-((triisopropylsilyl)oxy)phenyl)carbamate (61)

The crude 60 was dissolved in a 7:1:1:2 mixture of acetic acid/methanol/tetrahydrofuran/water (28:4:4:8 mL) and allowed to stir at room temperature.

After 3 hours, complete disappearance of starting material was observed by LC/MS. The reaction mixture was diluted with ethyl acetate and washed sequentially with water (2×500 mL), saturated aqueous sodium bicarbonate (200 mL) and brine. The organic phase was dried over magnesium sulphate filtered and excess ethyl acetate removed by rotary evaporation under reduced pressure. The resulting residue was subjected to flash column chromatography (silica gel, 25% ethyl acetate in hexane). Pure fractions were collected and combined and excess eluent was removed by rotary evaporation under reduced pressure to afford the desired product 61 (1 g, 71%). LC/MS, 3.70 min (ES+) m/z (relative intensity) 519.13 ([M+H]^(+.), 95); ¹H NMR (400 MHz, CDCl₃) δ 8.34 (s, 1H), 7.69 (s, 1H), 6.78 (s, 1H), 6.15 (s, 1H), 5.95 (ddt, J=17.2, 10.5, 5.7 Hz, 1H), 5.33 (dq, J=17.2, 1.5 Hz, 1H), 5.23 (ddd, J=10.4, 2.6, 1.3 Hz, 1H), 4.73 (tt, J=7.8, 4.8 Hz, 1H), 4.63 (dt, J=5.7, 1.4 Hz, 2H), 4.54 (s, 1H), 3.89-3.70 (m, 5H), 2.87 (dd, J=16.5, 10.5 Hz, 1H), 2.19 (dd, J=16.8, 4.6 Hz, 1H), 1.70 (d, J=1.3 Hz, 3H), 1.38-1.23 (m, 3H), 1.12 (s, 10H), 1.10 (s, 8H).

(c) (11S,11aS)-allyl 11-hydroxy-7-methoxy-2-methyl-5-oxo-8-((triisopropylsilyl)oxy)-11,11a -dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate (62)

Dimethyl sulphoxide (0.35 mL, 4.83 mmol, 2.5 eq) was added dropwise to a solution of oxalyl chloride (0.2 mL, 2.32 mmol, 1.2 eq) in dry dichloromethane (10 mL) at −78° C. (dry ice /acetone bath) under an atmosphere of argon. After 10 minutes a solution of 61 (1 g, 1.93 mmol) in dry dichloromethane (8 mL) was added slowly with the temperature still at −78° C. After 15 min triethylamine (1.35 mL, dried over 4 Å molecular sieves, 9.65 mmol, 5 eq) was added dropwise and the dry ice/acetone bath was removed. The reaction mixture was allowed to reach room temperature and was extracted with cold hydrochloric acid (0.1 M), saturated aqueous sodium bicarbonate and brine. The organic phase was dried over magnesium sulphate, filtered and excess dichloromethane was removed by rotary evaporation under reduced pressure to afford product 62 (658 mg, 66%). LC/MS, 3.52 min (ES+) m/z (relative intensity) 517.14 ([M+H]^(+.), 100); ¹H NMR (400 MHz, CDCl₃) δ 7.20 (s, 1H), 6.75-6.63 (m, J=8.8, 4.0 Hz, 2H), 5.89-5.64 (m, J=9.6, 4.1 Hz, 2H), 5.23-5.03 (m, 2H), 4.68-4.38 (m, 2H), 3.84 (s, 3H), 3.83-3.77 (m, 1H), 3.40 (s, 1H), 3.05-2.83 (m, 1H), 2.59 (d, J=17.1 Hz, 1H), 1.78 (d, J=1.3 Hz, 3H), 1.33-1.16 (m, 3H), 1.09 (d, J=2.2 Hz, 9H), 1.07 (d, J=2.1 Hz, 9H).

(d) (11S,11aS)-allyl 11-((tert-butyldimethylsilyl)oxy)-7-methoxy-2-methyl-5-oxo-8-((triisopropylsilyl)oxy)-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H) -carboxylate (63)

Tert-butyldimethylsilyltriflate (0.70 mL, 3.00 mmol, 3 eq) was added to a solution of compound 62 (520 mg, 1.00 mmol) and 2,6-lutidine (0.46 mL, 4.00 mmol, 4 eq) in dry dichloromethane (40 mL) at 0° C. under argon. After 10 min, the cold bath was removed and the reaction mixture was stirred at room temperature for 1 hour. The reaction mixture was extracted with water, saturated aqueous sodium bicarbonate and brine. The organic phase was dried over magnesium sulphate, filtered and excess was removed by rotary evaporation under reduced pressure. The resulting residue was subjected to flash column chromatography (silica gel; gradient, 10% ethyl acetate in hexane to 20% ethyl acetate in hexane). Pure fractions were collected and combined and excess eluent was removed by rotary evaporation under reduced pressure to give the product 63 (540 mg, 85%). LC/MS, 4.42 min (ES+) m/z (relative intensity) 653.14 ([M+Na]^(+.), 100); ¹H NMR (400 MHz, CDCl₃) δ 7.20 (s, 1H), 6.71-6.64 (m, J=5.5 Hz, 2H), 5.83 (d, J=9.0 Hz, 1H), 5.80-5.68 (m, J=5.9 Hz, 1H), 5.14-5.06 (m, 2H), 4.58 (dd, J=13.2, 5.2 Hz, 1H), 4.36 (dd, J=13.3, 5.5 Hz, 1H), 3.84 (s, 3H), 3.71 (td, J=10.1, 3.8 Hz, 1H), 2.91 (dd, J=16.9, 10.3 Hz, 1H), 2.36 (d, J=16.8 Hz, 1H), 1.75 (s, 3H), 1.31-1.16 (m, 3H), 1.12-1.01 (m, J=7.4, 2.1 Hz, 18H), 0.89-0.81 (m, 9H), 0.25 (s, 3H), 0.19 (s, 3H).

(e) (11S,11aS)-allyl 11-((tert-butyldimethylsilyl)oxy)-8-hydroxy-7-methoxy-2-methyl-5-oxo-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate (64)

Lithium acetate (87 mg, 0.85 mmol) was added to a solution of compound 63 (540 mg, 0.85 mmol) in wet dimethylformamide (6 mL, 50:1 DMF/water). After 4 hours, the reaction was complete and the reaction mixture was diluted with ethyl acetate (25 mL) and washed with aqueous citric acid solution (pH ˜3), water and brine. The organic layer was dried over magnesium sulphate filtered and excess ethyl acetate was removed by rotary evaporation under reduced pressure. The resulting residue was subjected to flash column chromatography (silica gel; gradient, 25% to 75% ethyl acetate in hexane). Pure fractions were collected and combined and excess eluent was removed by rotary evaporation under reduced pressure to give the product 64 (400 mg, quantitative). LC/MS, (3.33 min (ES+) m/z (relative intensity) 475.26 ([M+H]⁺, 100).

(f) (11S,11aS)-allyl 11-((tert-butyldimethylsilyl)oxy)-8-((5-iodopentyl)oxy)-7-methoxy-2-methyl-5-oxo-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate (65)

Diiodopentane (0.63 mL, 4.21 mmol, 5 eq) and potassium carbonate (116 mg, 0.84 mmol, 1 eq) were added to a solution of phenol 64 (400 mg, 0.84 mmol) in acetone (4 mL, dried over molecular sieves). The reaction mixture was then warmed to 60° C. and stirred for 6 hours. Acetone was removed by rotary evaporation under reduced pressure. The resulting residue was subjected to flash column chromatography (silica gel; 50/50, v/v, hexane/ethyl acetate,). Pure fractions were collected and combined and excess eluent was removed to provide 15 in 90% yield. LC/MS, 3.90 min (ES+) m/z (relative intensity) 670.91 ([M]⁺, 100). ¹H NMR (400 MHz, CDCl₃) δ 7.23 (s, 1H), 6.69 (s, 1H), 6.60 (s, 1H), 5.87 (d, J=8.8 Hz, 1H), 5.83-5.68 (m, J=5.6 Hz, 1H), 5.15-5.01 (m, 2H), 4.67-4.58 (m, 1H), 4.45-4.35 (m, 1H), 4.04-3.93 (m, 2H), 3.91 (s, 3H), 3.73 (td, J=10.0, 3.8 Hz, 1H), 3.25-3.14 (m, J=8.5, 7.0 Hz, 2H), 2.92 (dd, J=16.8, 10.3 Hz, 1H), 2.38 (d, J=16.8 Hz, 1H), 1.95-1.81 (m, 4H), 1.77 (s, 3H), 1.64-1.49 (m, 2H), 0.88 (s, 9H), 0.25 (s, 3H), 0.23 (s, 3H).

(iii) (11S,11aS)-4-(2-(1-((1-(allyloxy)-4-methyl-1,2-dioxopentan-3-yl)amino)-1-oxopropan-2-yl)hydrazinyl)benzyl 11-((tert-butyldimethylsilyl)oxy)-8-hydroxy-7-methoxy-2-methyl-5-oxo-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate (70)

(a) Allyl 3-(2-(2-(4-((((2-((S)-2-(((tert-butyldimethylsilyl)oxy)methyl)-4-methyl-2,3-dihydro-1H -pyrrole-1-carbonyl)-4-methoxy-5-((triisopropylsilyl)oxy)phenyl)carbamoyl)oxy)methyl)phenyl)hydrazinyl)propanamido)-4-methyl-2-oxopentanoate (66)

Triethylamine (2.23 mL, 18.04 mmol, 2.2 eq) was added to a stirred solution of the amine 59 (4 g, 8.20 mmol) and triphosgene (778 mg, 2.95 mmol, 0.36 eq) in dry tetrahydrofuran (40 mL) at 5° C. (ice bath). The progress of the isocyanate reaction was monitored by periodically removing aliquots from the reaction mixture and quenching with methanol and performing LC/MS analysis. Once the isocyanate formation was complete a solution of the alloc-Val-Ala-PABOH (4.12 g, 12.30 mmol, 1.5 eq) and triethylamine (1.52 mL, 12.30 mmol, 1.5 eq) in dry tetrahydrofuran (40 mL) was rapidly added by injection to the freshly prepared isocyanate. The reaction mixture was allowed to stir at 40° C. for 4 hours. Excess solvent was removed by rotary evaporation under reduced pressure. The resulting residue was subjected to flash column chromatography (silica gel; gradient, 1% methanol to 5% methanol in dichloromethane). (Alternative chromatography conditions using EtOAc and Hexane have also been successful). Pure fractions were collected and combined and excess eluent was removed by rotary evaporation under reduced pressure to give the product 66 (3.9 g, 50%). LC/MS, 4.23 min (ES+) m/z (relative intensity) 952.36 ([M+H]^(+.) , 100); ¹H NMR (400 MHz, CDCl₃) δ 8.62 (br s, 1H), 8.46 (s, 1H), 7.77 (br s, 1H), 7.53 (d, J=8.4 Hz, 2H), 7.32 (d, J=8.5 Hz, 2H), 6.76 (s, 1H), 6.57 (d, J=7.6 Hz, 1H), 6.17 (s, 1H), 6.03-5.83 (m, 1H), 5.26 (dd, J=33.8, 13.5 Hz, 3H), 5.10 (s, 2H), 4.70-4.60 (m, 2H), 4.58 (dd, J=5.7, 1.3 Hz, 2H), 4.06-3.99 (m, 1H), 3.92 (s, 1H), 3.82-3.71 (m, 1H), 3.75 (s, 3H), 2.79-2.64 (m, 1H), 2.54 (d, J=12.9 Hz, 1H), 2.16 (dq, J=13.5, 6.7 Hz, 1H), 1.67 (s, 3H), 1.46 (d, J=7.0 Hz, 3H), 1.35-1.24 (m, 3H), 1.12 (s, 9H), 1.10 (s, 9H), 0.97 (d, J=6.8 Hz, 3H), 0.94 (d, J=6.8 Hz, 3H), 0.87 (s, 9H), 0.07-−0.02 (m, 6H).

(b) Allyl 3-(2-(2-(4-((((2-((S)-2-(hydroxymethyl)-4-methyl-2,3-dihydro-1H-pyrrole-1-carbonyl)-4-methoxy-5-((triisopropylsilyl)oxy)phenyl)carbamoyl)oxy)methyl)phenyl)hydrazinyl)propanamido)-4-methyl-2-oxopentanoate (67)

The TBS ether 66 (1.32 g, 1.38 mmol) was dissolved in a 7:1:1:2 mixture of acetic acid/methanol/tetrahydrofuran/water (14:2:2:4 mL) and allowed to stir at room temperature. After 3 hours no more starting material was observed by LC/MS. The reaction mixture was diluted with ethyl acetate (25 mL) and washed sequentially with water, saturated aqueous sodium bicarbonate and brine. The organic phase was dried over magnesium sulphate filtered and excess ethyl acetate removed by rotary evaporation under reduced pressure. The resulting residue was subjected to flash column chromatography (silica gel, 2% methanol in dichloromethane). Pure fractions were collected and combined and excess eluent was removed by rotary evaporation under reduced pressure to afford the desired product 67 (920 mg, 80%). LC/MS, 3.60 min (ES+) m/z (relative intensity) 838.18 ([M+H]^(+.), 100). ¹H NMR (400 MHz, CDCl₃) δ 8.55 (s, 1H), 8.35 (s, 1H), 7.68 (s, 1H), 7.52 (d, J=8.1 Hz, 2H), 7.31 (d, J=8.4 Hz, 2H), 6.77 (s, 1H), 6.71 (d, J=7.5 Hz, 1H), 6.13 (s, 1H), 5.97-5.82 (m, J=5.7 Hz, 1H), 5.41-5.15 (m, 3H), 5.10 (d, J=3.5 Hz, 2H), 4.76-4.42 (m, 5H), 4.03 (t, J=6.6 Hz, 1H), 3.77 (s, 5H), 2.84 (dd, J=16.7, 10.4 Hz, 1H), 2.26-2.08 (m, 2H), 1.68 (s, 3H), 1.44 (d, J=7.0 Hz, 3H), 1.30 (dt, J=14.7, 7.4 Hz, 3H), 1.12 (s, 9H), 1.10 (s, 9H), 0.96 (d, J=6.8 Hz, 3H), 0.93 (d, J=6.8 Hz, 3H).

(c) (11S,11aS)-4-(2-(1-((1-(allyloxy)-4-methyl-1,2-dioxopentan-3-yl)amino)-1-oxopropan-2-yl)hydrazinyl)benzyl 11-hydroxy-7-methoxy-2-methyl-5-oxo-8-((triisopropylsilyl)oxy)-11,11a -dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate (68)

Dimethyl sulphoxide (0.2 mL, 2.75 mmol, 2.5 eq) was added dropwise to a solution of oxalyl chloride (0.11 mL, 1.32 mmol, 1.2 eq) in dry dichloromethane (7 mL) at −78° C. (dry ice /acetone bath) under an atmosphere of argon. After 10 minutes a solution of 67 (920 mg, 1.10 mmol) in dry dichloromethane (5 mL) was added slowly with the temperature still at −78° C. After 15 min triethylamine (0.77 mL, dried over 4 Å molecular sieves, 5.50 mmol, 5 eq) was added dropwise and the dry ice/acetone bath was removed. The reaction mixture was allowed to reach room temperature and was extracted with cold hydrochloric acid (0.1 M), saturated aqueous sodium bicarbonate and brine. The organic phase was dried over magnesium sulphate, filtered and excess dichloromethane was removed by rotary evaporation under reduced pressure. The resulting residue was subjected to column flash chromatography (silica gel; gradient 2% methanol to 5% methanol in dichloromethane). Pure fractions were collected and combined and removal of excess eluent by rotary evaporation under reduced pressure afforded the product 68 (550 mg, 60%). LC/MS, 3.43 min (ES+) m/z (relative intensity) 836.01 ([M]^(+.), 100). ¹H NMR (400 MHz, CDCl₃) δ 8.39 (s, 1H), 7.52-7.40 (m, 2H), 7.21-7.08 (m, J=11.5 Hz, 2H), 6.67 (s, 1H), 6.60-6.47 (m, J=7.4 Hz, 1H), 5.97-5.83 (m, 1H), 5.79-5.66 (m, 1H), 5.38-4.90 (m, 6H), 4.68-4.52 (m, J =18.4, 5.5 Hz, 4H), 4.04-3.94 (m, J=6.5 Hz, 1H), 3.87-3.76 (m, 5H), 3.00-2.88 (m, 1H), 2.66-2.49 (m, 2H), 2.21-2.08 (m, 2H), 1.76 (s, 3H), 1.45 (d, J=7.0 Hz, 3H), 1.09-0.98 (m, J=8.9 Hz, 18H), 0.96 (d, J=6.7 Hz, 3H), 0.93 (d, J=6.9 Hz, 3H).

(d) (11S,11aS)-4-(2-(1-((1-(Allyloxy)-4-methyl-1,2-dioxopentan-3-yl)amino)-1-oxopropan-2-yl)hydrazinyl)benzyl 11-((tert-butyldimethylsilyl)oxy)-7-methoxy-2-methyl-5-oxo-8-((triisopropylsilyl)oxy)-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H) -carboxylate (69)

Tert-butyldimethylsilyltriflate (0.38 mL, 1.62 mmol, 3 eq) was added to a solution of compound 68 (450 mg, 0.54 mmol) and 2,6-lutidine (0.25 mL, 2.16 mmol, 4 eq) in dry dichloromethane (5 mL) at 0° C. under argon. After 10 min, the cold bath was removed and the reaction mixture was stirred at room temperature for 1 hour. The reaction mixture was extracted with water, saturated aqueous sodium bicarbonate and brine. The organic phase was dried over magnesium sulphate, filtered and excess solvent was removed by rotary evaporation under reduced pressure. The resulting residue was subjected to column flash chromatography (silica gel; 50/50 v/v hexane/ethyl acetate). Pure fractions were collected and combined and excess eluent was removed by rotary evaporation under reduced pressure to give the product 69 (334 mg, 65%). LC/MS, 4.18 min (ES+) m/z (relative intensity) 950.50 ([M]^(+.), 100). ¹H NMR (400 MHz, CDCl₃) δ 8.53 (s, 1H), 8.02 (s, 1H), 7.44 (d, J=7.6 Hz, 2H), 7.21 (s, 1H), 7.08 (d, J=8.2 Hz, 2H), 6.72-6.61 (m, J=8.9 Hz, 2H), 6.16 (s, 1H), 5.97-5.79 (m, J=24.4, 7.5 Hz, 2H), 5.41-5.08 (m, 5H), 4.86 (d, J=12.5 Hz, 1H), 4.69-4.60 (m, 1H), 4.57 (s, 1H), 4.03 (t, J=6.7 Hz, 1H), 3.87 (s, 3H), 3.74 (td, J=9.6, 3.6 Hz, 1H), 2.43-2.09 (m, J=34.8, 19.4, 11.7 Hz, 3H), 1.76 (s, 3H), 1.43 (d, J=6.9 Hz, 3H), 1.30-1.21 (m, 3H), 0.97 (d, J=6.7 Hz, 3H), 0.92 (t, J=8.4 Hz, 3H), 0.84 (s, 9H), 0.23 (s, 3H), 0.12 (s, 3H).

(e) (11S,11aS)-4-(2-(1-((1-(Allyloxy)-4-methyl-1,2-dioxopentan-3-yl)amino)-1-oxopropan-2-yl)hydrazinyl)benzyl 11-((tert-butyldimethylsilyl)oxy)-8-hydroxy-7-methoxy-2-methyl-5-oxo-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate (70)

Lithium acetate (50 mg, 0.49 mmol) was added to a solution of compound 69 (470 mg, 0.49 mmol) in wet dimethylformamide (4 mL, 50:1 DMF/water). After 4 hours, the reaction was complete and the reaction mixture was diluted with ethyl acetate and washed with citric acid (pH ˜3), water and brine. The organic layer was dried over magnesium sulphate filtered and excess ethyl acetate was removed by rotary evaporation under reduced pressure. The resulting residue was subjected to column flash chromatography (silica gel; gradient, 50/50 to 25/75 v/v hexane/ethyl acetate). Pure fractions were collected and combined and excess eluent was removed by rotary evaporation under reduced pressure to give the product 70 (400 mg, quantitative). LC/MS, 3.32 min (ES+) m/z (relative intensity) 794.18 ([M+H]^(+.), 100). ¹H NMR (400 MHz, CDCl₃) δ 8.53 (s, 1H), 8.02 (s, 1H), 7.44 (d, J=7.6 Hz, 2H), 7.21 (s, 1H), 7.08 (d, J=8.2 Hz, 2H), 6.72-6.61 (m, J=8.9 Hz, 2H), 6.16 (s, 1H), 5.97-5.79 (m, J=24.4, 7.5 Hz, 2H), 5.41-5.08 (m, 5H), 4.86 (d, J=12.5 Hz, 1H), 4.69-4.60 (m, 1H), 4.57 (s, 1H), 4.03 (t, J=6.7 Hz, 1H), 3.87 (s, 3H), 3.74 (td, J=9.6, 3.6 Hz, 1H), 2.43-2.09 (m, J =34.8, 19.4, 11.7 Hz, 3H), 1.76 (s, 3H), 1.43 (d, J=6.9 Hz, 3H), 1.30-1.21 (m, 3H), 0.97 (d, J=6.7 Hz, 3H), 0.92 (t, J=8.4 Hz, 3H), 0.84 (s, 9H), 0.23 (s, 3H), 0.12 (s, 3H).

(iv) (11S)-4-(2-(1-((1-amino-3-methyl-1-oxobutan-2-yl)amino)-1-oxopropan-2-yl)hydrazinyl)benzyl 11-hydroxy-7-methoxy-8-((5-((7-methoxy-2-methyl-5-oxo-5,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yl)oxy)pentyl)oxy)-2-methyl-5-oxo-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate (73)

(a) (11S)-allyl 8-((5-(((11S)-10-(((4-(2-(1-((1-(allyloxy)-4-methyl-1,2-dioxopentan-3-yl)amino)-1-oxopropan-2-yl)hydrazinyl)benzyl)oxy)carbonyl)-11-((tert-butydimethylsilyl)oxy)-7-methoxy-2-methyl-5-oxo-5,10,11,11a-tetrahydrodro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yl)oxy)pentyl)oxy)-11-((tert-butyldimethysilyl)oxy)-7-methoxy-2-methyl-5-oxo-11,11a -dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate (71)

Potassium carbonate (70 mg, 0.504 mmol, 1 eq) was added to a solution of 65 (370 mg, 0.552 mmol, 1.2 eq) and phenol 70 (400 mg, 0.504 mmol) in dry acetone (25 mL). The reaction was stirred 8 hours at 70° C. The LC/MS showed that all the starting material was not consumed, so the reaction was allowed to stir overnight at room temperature and stirred for an additional 2 hours the next day. Acetone was removed by rotary evaporation under reduced pressure. The resulting residue was subjected to flash column chromatography (silica gel; 80% ethyl acetate in hexane to 100% ethyl acetate). Pure fractions were collected and combined and excess eluent was removed by rotary evaporation under reduced pressure to give the product 71 (385 mg, 57%). LC/MS, 4.07 min (ES+) m/z (relative intensity) 1336.55 ([M+H]^(+.), 50).

(b) (11S)-allyl 8-((5-(((11S)-10-(((4-(2-(1-((1-(allyloxy)-4-methy-1,2-dioxopentan-3-yl)amino)-1-oxopropan-2-yl)hydrazinyl)benzyl)oxy)carbonyl)-11-hydroxy-7-methoxy-2-methy-5-oxo-5,10,11,11a-tetrahydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yl)oxy)pentyl)oxy)-11-hydroxy-7-methoxy-2-methyl-5-oxo-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate (72)

Tetra-n-butylammonium fluoride (1M, 0.34 mL, 0.34 mmol, 2 eq) was added to a solution of 71 (230 mg, 0.172 mmol) in dry tetrahydrofuran (3 mL). The starting material was totally consumed after 10 minutes. The reaction mixture was diluted with ethyl acetate (30 mL) and washed sequentially with water and brine. The organic phase was dried over magnesium sulphate filtered and excess ethyl acetate removed by rotary evaporation under reduced pressure. The resulting residue 72 was used as a crude mixture for the next reaction. LC/MS, 2.87 min (ES+) m/z (relative intensity) 1108.11 ([M+H]^(+.), 100).

(c) (11S)-4-(2-(1-((1-amino-3-methyl-1-oxobutan-2-yl)amino)-1-oxopropan-2-yl)hydrazinyl)benzyl 11-hydroxy-7-methoxy-8-((5-((7-methoxy-2-methyl-5-oxo-5,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yl)oxy)pentyl) oxy)-2-methyl-5-oxo-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10 (5H)-carboxylate (73)

Tetrakis(triphenylphosphine)palladium(0) (12 mg, 0.01 mmol, 0.06 eq) was added to a solution of crude 72 (0.172 mmol) and pyrrolidine (36 μL, 0.43 mmol, 2.5 eq) in dry dichloromethane (10 mL). The reaction mixture was stirred 20 minutes and diluted with dichloromethane and washed sequentially with saturated aqueous ammonium chloride and brine. The organic phase was dried over magnesium sulphate filtered and excess dichloromethane removed by rotary evaporation under reduced pressure. The resulting residue 73 was used as a crude mixture for the next reaction. LC/MS, 2.38 min (ES+) m/z (relative intensity) 922.16 ([M+H]^(+.), 40).

(v) Key Intermediates (a) 1-iodo-2-oxo-6, 9,12,15-octaoxa-3-azatriacontan-30-oic acid (75)

A solution of iodoacetic anhydride (0.088 g, 0.249 mmol, 1.1 eq) in dry DCM (1 mL) was added to amino-PEG₍₈₎-acid 74 (0.100 g, 0.226 mmol, 1.0 eq) in DCM (1 mL). The mixture was stirred in the dark at room temperature for 4 hours. The reaction mixture was washed with 5% citric acid, water, dried over MgSO₄, filtered and concentrated under reduced pressure. The residue was purified by flash chromatography (silica gel, 3% MeOH and 0.1% formic acid in chloroform to 10% MeOH and 0.1% formic acid in chloroform) to afford the product as a clear oil (0.068 g, 49%). LC/MS (1.13 min (ES⁺)) (System 1), m/z: 610.15 [M+H]⁺. ¹H NMR (400 MHz, CDCl₃) δ 7.04 (brs, 1H), 3.78 (t, J=6.0 Hz, 2H,), 3.74 (s, 2H), 3.68-3.64 (m, 28H), 3.60-3.56 (m, 2H), 3.46 (dd, J=10.2 Hz, 5.3 Hz, 2H), 2.61 (t, J=6.0 Hz, 2H).

(b) 1-bromo-2-oxo-6,9,12,15-octaoxa-3-azatriacontan-30-oic acid (76)

A solution of bromoacetic anhydride (0.065 g, 0.249 mmol, 1.1 eq) in dry DCM (1 mL) was added to amino-PEG₍₈₎-acid 74 (0.100 g, 0.226 mmol, 1.0 eq) in DCM (1 mL). The mixture was stirred in the dark at room temperature for 4 hours. The reaction mixture was washed with 5% citric acid, water, dried over MgSO₄, filtered and concentrated under reduced pressure. The residue was purified by flash chromatography (silica gel, 3% MeOH and 0.1% formic acid in chloroform to 10% MeOH and 0.1% formic acid in chloroform) to afford the product as a pale orange oil (0.050 g, 39%). LC/MS (1.08 min (ES⁺)) (System 1), m/z: 562.20 [M]⁺ 564.15 [M+2]⁺. ¹H NMR (400 MHz, CDCl₃) δ 7.28 (brs, 1H), 3.87 (s, 2H), 3.76 (t, J=6.1 Hz, 2H), 3.68-3.60 (m, 28H), 3.60-3.56 (m, 2H), 3.47 (dd, J=10.3 Hz, 5.2 Hz, 2H), 2.59 (t, J=6.1 Hz, 2H).

General Experimental Methods for Steps (vi) and (vii)

LC/MS data were obtained using a Shimadzu Nexera series LC/MS with a Shimadzu LC/MS-2020 quadrupole MS, with Electrospray ionisation. Mobile phase A—0.1% formic acid in water. Mobile phase B—0.1% formic acid in acetonitrile. Flow rate of 0.80 ml/min. Gradient from 5% B rising up to 100% B over 2.00 min, remaining at 100% B for 0.50 min and then back down to 5% B over 0.05 min (held for 0.45 min). The total run time is 3 min. Column: Waters, Aquity UPLC BEH Shield RP18 1.7 μm, 2.1×50 mm; (System 1).

Or, gradient from 5% B rising up to 100% B over 10.00 min, remaining at 100% B for 2.00 min and then back down to 5% B over 0.10 minutes (held for 2.90 min). The total run time is 15 minutes. Column: Phenomenex, Gemini-NX 3u C18 110A, 100×2.00 mm; (System 2). Chromatograms based on UV detection at 254 nm. Mass Spectra were achieved using the MS in positive mode.

HPLC analyses were carried out on HPLC system: Shimadzu Prominence series with UV/VIS detector (SPD-20A) and fraction collector (FRC-10A). Mobile phase A—0.1% formic acid in water. Mobile phase B—0.1% formic acid in acetonitrile. Gradient (applicable to analytical and preparative systems) from 0% B rising up to 100% B over 15.00 min, remaining at 100% B for 2.00 min and then down to 13% B over 1.10 min. Analytical analysis, column: Phenomenex, Gemini-NX 5μ C18 110A, 150×4.60 mm and flow rate of 1.00 ml/min (System 3). Preparative analysis, column: Phenomenex, Gemini-NX 5μ C18 110A, 150×21.20 mm and flow rate of 20.00 ml/min. (System 4)

(vi) (11S,11aS)-4-((32S,35S)-1-iodo-32-isopropyl-35-methyl-2,30,33-trioxo-6,9,12,15-octaoxa-3,31,34-triazahexatriacontanamido)benzyl 11-hydroxy-7-methoxy-8-((5-(((S)-7-methoxy-2-methyl-5-oxo-5,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yl)oxy)pentyl)oxy)-2-methyl-5-oxo-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate (77, D)

N,N′-diisopropylcarbodiimide (DIC, 9.22 μL, 0.059 mmol, 1.1 eq) was added to a solution of amine 73 (0.054 mmol, 1.1 eq) and iodo-(PEG)₈-acid 75 (39.6 mg, 0.065 mmol, 1.2 eq) in dry dichloromethane (5 mL). The reaction was stirred overnight until the presence of starting material was no longer observed by LC/MS. The reaction was diluted with dichloromethane and washed sequentially with water and brine. The organic phase was dried over magnesium sulphate filtered and excess dichloromethane removed by rotary evaporation under reduced pressure. The resulting residue was subjected to flash column chromatography (silica gel; 100% chloroform to 5% methanol in chloroform). Fractions containing the product were collected and combined and excess eluent was removed by rotary evaporation under reduced pressure, this was subjected to further purification using reverse-phase preparative HPLC (System 4). Pure fractions were collected using the fraction collector, combined and the desired product lyophilised to give 77, D (15.8 mg, 19% over 3 steps). LC-MS, System 1, 1.44 min (ES+) m/z 1513.60 [M+H]⁺. ¹H NMR (400 MHz, CDCl₃) δ 8.82 (s, 1H), 7.92-7.78 (m, 1H), 7.64 (d, J=7.0 Hz, 2H), 7.50 (s, 1H), 7.23-6.98 (m, 6H), 6.81 (s, 1H), 6.75 (s, 1H), 6.69 (s, 1H), 6.46 (s, 1H), 5.76 (d, J=8.3 Hz, 1H), 5.32 (m, 1H), 4.73 (d, J=11.3 Hz, 1H), 4.67-4.54 (m, 1H), 4.42 (br s, 1H), 4.32-4.19 (m, 2H), 4.18-3.99 (m, 4H), 3.91 (s, 3H), 3.87 (s, 3H), 3.84-3.76 (m, 3H), 3.71 (s, 2H), 3.70-3.58 (m, 28H), 3.56 (dd, J=10.1, 5.1 Hz, 2H), 3.43 (dd, J=10.0, 5.1 Hz, 1H), 3.25-3.12 (m, 1H), 3.06-2.87 (m, 2H), 2.73-2.41 (m, 4H), 2.33-1.97 (m, 3H), 1.96-1.71 (m, 4H), 1.84 (s, 3H), 1.78 (s, 3H), 1.71-1.51 (m, 2H), 1.49-1.22 (m, 3H), 1.07-0.85 (m, 6H).

(vii) (11S,11aS)-4-((32S,35S)-1-bromo-32-isopropyl-35-methyl-2,30,33-trioxo-6,9,12,15-octaoxa-3,31,34-triazahexatriacontanamido)benzyl 11-hydroxy-7-methoxy-8-((5-(((S)-7-methoxy-2-methyl-5-oxo-5,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yl)oxy)pentyl)oxy)-2-methyl-5-oxo-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate (78, E)

N,N′-diisopropylcarbodiimide (DIC, 9.22 μL, 0.059 mmol, 1.1 eq) was added to a solution of amine 73 (0.054 mmol, 1.1 eq) and bromo-(PEG)₈-acid 76 (36.5 mg, 0.065 mmol, 1.2 eq) in dry dichloromethane (5 mL). The reaction was stirred overnight until the presence of starting material was no longer observed by LC/MS. The reaction was diluted with dichloromethane and washed sequentially with water and brine. The organic phase was dried over magnesium sulphate filtered and excess dichloromethane removed by rotary evaporation under reduced pressure. The resulting residue was purified using reversed-phase preparative HPLC (System 4). Pure fractions were collected using the fraction collector, combined and the desired product lyophilised to give 78, E (26.6 mg, 33% over 3 steps). LC-MS, System 1, 1.44 min (ES+) m/z 1466.85 [M]⁺. ¹H NMR (400 MHz, CDCl₃) δ 8.82 (s, 1H), 7.87 (s, 1H), 7.64 (d, J=7.0 Hz, 2H), 7.50 (s, 1H), 7.23-6.98 (m, 6H), 6.81 (s, 1H), 6.74 (s, 1H), 6.69 (s, 1H), 6.45 (s, 1H), 5.75 (d, J=9.2 Hz, 1H), 5.32 (d, J=11.2 Hz, 1H), 4.72 (d, J =11.7 Hz, 1H), 4.68-4.52 (m, 1H), 4.35 (br s, 1H), 4.32-4.17 (m, 2H), 4.17-3.99 (m, 4H), 3.90 (s, 3H), 3.87 (s, 3H), 3.84-3.74 (m, 3H), 3.72-3.58 (m, 32H), 3.46 (dd, J=10.1, 5.1 Hz, 2H), 3.25-3.09 (m, 1H), 3.05-2.84 (m, 2H), 2.75-2.40 (m, 3H), 2.34-1.98 (m, 3H), 1.96-1.71 (m, 4H), 1.83 (s, 3H), 1.77 (s, 3H), 1.67-1.52 (m, 2H), 1.48-1.20 (m, 3H), 1.09-0.88 (m, 6H).

Example 6 Activity of Released Compounds

K562 Assay

K562 human chronic myeloid leukaemia cells were maintained in RPM1 1640 medium supplemented with 10% fetal calf serum and 2 mM glutamine at 37° C. in a humidified atmosphere containing 5% CO₂ and were incubated with a specified dose of drug for 1 hour or 96 hours at 37° C. in the dark. The incubation was terminated by centrifugation (5 min, 300 g) and the cells were washed once with drug-free medium. Following the appropriate drug treatment, the cells were transferred to 96-well microtiter plates (10⁴ cells per well, 8 wells per sample). Plates were then kept in the dark at 37° C. in a humidified atmosphere containing 5% CO₂. The assay is based on the ability of viable cells to reduce a yellow soluble tetrazolium salt, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT, Aldrich-Sigma), to an insoluble purple formazan precipitate. Following incubation of the plates for 4 days (to allow control cells to increase in number by approximately 10 fold), 20 μL of MTT solution (5 mg/mL in phosphate-buffered saline) was added to each well and the plates further incubated for 5 h. The plates were then centrifuged for 5 min at 300 g and the bulk of the medium pipetted from the cell pellet leaving 10-20 μL per well. DMSO (200 μL) was added to each well and the samples agitated to ensure complete mixing. The optical density was then read at a wavelength of 550 nm on a Titertek Multiscan ELISA plate reader, and a dose-response curve was constructed. For each curve, an IC₅₀ value was read as the dose required to reduce the final optical density to 50% of the control value.

Compound RelC has an IC₅₀ of 0.425 nM in this assay.

Example 7 Formation of Conjugates

General Antibody Conjugation Procedure

Antibodies are diluted to 1-5 mg/mL in a reduction buffer (examples: phosphate buffered saline PBS, histidine buffer, sodium borate buffer,TRIS buffer). A freshly prepared solution of TCEP (tris(2-carboxyethyl)phosphine hydrochloride) is added to selectively reduce cysteine disulfide bridges. The amount of TCEP is proportional to the target level of reduction, within 1 to 4 molar equivalents per antibody, generating 2 to 8 reactive thiols. After reduction for several hours at 37° C., the mixture is cooled down to room temperature and excess drug-linker added as a diluted DMSO solution (final DMSO content of up to 10% volume/volume of reaction mixture). The mixture was gently shaken at either 4° C. or room temperature for the appropriate time, generally 1-3 hours. Excess reactive thiols can be reacted with a ‘thiol capping reagent’ like N-ethyl maleimide (NEM) at the end of the conjugation. Antibody-drug conjugates are concentrated using centrifugal spin-filters with a molecular weight cut-off of 10 kDa or higher, then purified by tangential flow filtration (TFF) or Fast Protein Liquid Chromatography (FPLC). Corresponding antibody-drug conjugates can be determined by analysis by High-Performance Liquid Chromatography (HPLC) or Ultra-High-Performance Liquid Chromatography (UHPLC) to assess drug-per-antibody ratio (DAR) using reverse-phase chromatography (RP) or Hydrophobic-Interaction Chromatography (HIC), coupled with UV-Visible, Fluorescence or Mass-Spectrometer detection; aggregate level and monomer purity can be analysed by HPLC or UHPLC using size-exclusion chromatography coupled with UV-Visible, Fluorescence or Mass-Spectrometer detection. Final conjugate concentration is determined by a combination of spectroscopic (absorbance at 280, 214 and 330 nm) and biochemical assay (bicinchonic acid assay BCA; Smith, P. K., et al. (1985) Anal. Biochem. 150 (1): 76-85; using a known-concentration IgG antibody as reference). Antibody-drug conjugates are generally sterile filtered using 0.2 μm filters under aseptic conditions, and stored at +4° C., −20° C. or −80° C.

DAR Determination

Antibody or ADC (ca. 35 μg in 35 μL) was reduced by addition of 10 μL borate buffer (100 mM, pH 8.4) and 5 μL DTT (0.5 M in water), and heated at 37° C. for 15 minutes. The sample was diluted with 1 volume of acetonitrile: water: formic acid (49%: 49%: 2% v/v), and injected onto a Widepore 3.6μ XB-C18 150×2.1 mm (P/N 00F-4482-AN) column (Phenomenex Aeris) at 80° C., in a UPLC system (Shimadzu Nexera) with a flow rate of 1 ml/min equilibrated in 75% Buffer A (Water, Trifluoroacetic acid (0.1% v/v) (TFA), 25% buffer B (Acetonitrile: water: TFA 90%: 10%: 0.1% v/v). Bound material was eluted using a gradient from 25% to 55% buffer B in 10 min. Peaks of UV absorption at 214 nm were integrated. The following peaks were identified for each ADC or antibody: native antibody light chain (L0), native antibody heavy chain (H0), and each of these chains with added drug-linkers (labelled L1 for light chain with one drug and H1, H2, H3 for heavy chain with 1, 2 or 3 attached drug-linkers). The UV chromatogram at 330 nm was used for identification of fragments containing drug-linkers (i.e., L1, H1, H2, H3).

A PBD/protein molar ratio was calculated for both light chains and heavy chains:

${\frac{Drug}{Protein}{ratio}\mspace{14mu}{on}\mspace{14mu}{light}\mspace{14mu}{chain}} = \frac{\%\mspace{14mu}{Area}\mspace{14mu}{at}\mspace{14mu} 214\mspace{14mu}{nm}\mspace{14mu}{for}\mspace{14mu} L\; 1}{\%\mspace{14mu}{Area}\mspace{14mu}{at}\mspace{14mu} 214\mspace{14mu}{nm}\mspace{14mu}{for}\mspace{14mu} L\; 0\mspace{14mu}{and}\mspace{14mu} L\; 1}$ ${\frac{Drug}{Protein}{ratio}\mspace{14mu}{on}\mspace{14mu}{heavy}\mspace{14mu}{chain}} = \frac{\sum\limits_{n = 0}^{3}\;{n \times \left( {\%\mspace{14mu}{area}\mspace{14mu}{at}\mspace{14mu} 214\mspace{14mu}{for}\mspace{14mu}{Hn}} \right)}}{\sum\limits_{n = 0}^{3}{\%\mspace{14mu}{area}\mspace{14mu}{at}\mspace{14mu} 214\mspace{14mu}{for}\mspace{14mu}{Hn}}}$

Final DAR is calculated as:

${DAR} = {2 \times \left( {{\frac{Drug}{Protein}{ratio}\mspace{14mu}{on}\mspace{14mu}{light}\mspace{14mu}{chain}} + {\frac{Drug}{Protein}{ratio}\mspace{14mu}{on}\mspace{14mu}{heavy}\mspace{14mu}{chain}}} \right)}$

DAR measurement is carried out at 214 nm because it minimises interference from drug-linker absorbance.

Generation of ADC (J591-E)

To J591, comprising a variable domain which is SEQ ID NO. 3 paired with SEQ ID NO. 4, (33.3 mg, 222 nanomoles) in 4.83 mL PBS, EDTA was added to a final concentration of 2.0 mM EDTA. The antibody was reduced for 4 hours at room temperature by a solution of TCEP (40 eq, 889 L at 10 mM, 8890 nanomoles), then dialysed overnight against PBS, 2.5 mM EDTA. Ca. 8 mL of antibody at 2.9 mg/mL was recovered (23 mg, 70%) then the antibody was reoxidised by adding 20 eq dhaa (dehydroascorbic acid, fresh 50 mM solution in DMA, 89 μL, 4 micromoles). Reoxidation was carried out at room temperature for 3 hours, the antibody batch was dialysed overnight into 10 mM sodium borate pH 8.4 containing 2.5 mM EDTA. Antibody is sterile filtered, then split in four aliquot. To one aliquot (1 mL at 3.0 mg/mL=3.0 mg, 20.0 nanomoles) was diluted to 3 mL of 10 mM sodium borate, 2 mM EDTA pH 8.4; compound E was added as a DMSO solution (20 molar equivalent/antibody, 400 nanomoles, in 0.3 mL DMSO) in two fractions overnight. The solution was kept at room temperature, then the conjugation was quenched by addition of N-acetyl cysteine (0.8 micromoles, 80 μL at 10 mM), then injected into an AKTA™ Pure FPLC using a GE Healthcare HiLoad™ 26/600 column packed with Superdex 200 PG, eluting with 2.6 mL/min of sterile-filtered phosphate-buffered saline (PBS). Fractions corresponding to J591-E monomer peak were pooled, concentrated using a 15 mL Amicon Ultracell 50 KDa MWCO spin filter, analysed and sterile-filtered.

UHPLC analysis on a Shimadzu Prominence system using a Phenomenex Aeris 3.6u XB-C 18 150×2.1 mm column eluting with a gradient of water and acetonitrile on a reduced sample of J591-E at 280 nm and 330 nm (Compound E specific) shows a mixture of light and heavy chains attached to several molecules of compound E, consistent with a drug-per-antibody ratio (DAR) of 1.0 molecules of compound E per antibody.

UHPLC analysis on a Shimadzu Prominence system using a Tosoh TSKgel G3000 SWCL 5 um 7.8×300 mm 300×4.60 mm eluting with sterile-filtered SEC buffer containing 200 mM potassium phosphate pH 6.95, 250 mM potassium chloride and 10% isopropanol (v/v) on a sample of J591-E at 280 nm shows a monomer purity of over 91.6%. UV/Vis concentration assay gives a final amount of J591-E of 1.0 mg (33% yield).

Generation of ADC (J591-C)

To J591 (15.3 mg, 102 nanomoles) in PBS, EDTA and DTT solutions were added to a final concentration of 1.5 mM EDTA and 3 mM DTT. The antibody was reduced overnight (ca. 16 h) at room temperature, then diluted with 45 mL 20 mM sodium succinate pH 5.0, loaded on a GE Healthcare HiTrap SP FF Column 1 mL using an Akta system. Antibody was eluted out using 50 mM Tris-HCl pH 7.5, 150 mM NaCl and the elute was buffer exchanged by dialysis with 100 mM NaPO4, 2.5 mM EDTA. The antibody was then reoxidised by adding 20 eq dhaa (dehydroascorbic acid, fresh 20 mM solution in DMA, 100 μL, 2 micromoles). Reoxidation was carried out at room temperature for 3 hours and compound C was added as a DMSO solution (10.0 molar equivalent/antibody, 10000 nanomoles, in 0.9 mL DMSO). The solution was mixed for 1.5 hours at room temperature, then the conjugation was quenched by addition of N-acetyl cysteine (4 micromoles, 400 μL at 10 mM), then injected into an AKTA™ Pure FPLC using a GE Healthcare HiLoad™ 26/600 column packed with Superdex 200 PG, eluting with 2.6 mL/min of sterile-filtered phosphate-buffered saline (PBS). Fractions corresponding to J591-C monomer peak were pooled, concentrated using a 15 mL Amicon Ultracell 50 KDa MWCO spin filter, analysed and sterile-filtered. The batch was then mixed with a previously made batch of the same ADC from 5 mg antibody. UHPLC analysis on a Shimadzu Prominence system using a Phenomenex Aeris 3.6u XB-C18 150×2.1 mm column eluting with a gradient of water and acetonitrile on a reduced sample of J591-C at 280 nm and 330 nm (Compound C specific) shows a mixture of light and heavy chains attached to several molecules of compound C, consistent with a drug-per-antibody ratio (DAR) of 1.88 molecules of compound C per antibody.

UHPLC analysis on a Shimadzu Prominence system using a Tosoh TSKgel G3000 SWCL 5 um 7.8×300 mm 300×4.60 mm eluting with sterile-filtered SEC buffer containing 200 mM potassium phosphate pH 6.95, 250 mM potassium chloride and 10% isopropanol (v/v) on a sample of J591-C at 214 nm shows a monomer purity of over 98.1% with 1.8% dimer. HPLC concentration assay gives a concentration of final J591-C at 0.74 mg/mL in 12.0 mL, obtained mass of J591-C is 8.85 mg (44% combined yield from 15 mg and 5 mg antibody).

In Vitro Cytotoxicity

The efficacy of the J591-C and J-591E conjugates was tested against LNCaP cells as described above:

GI₅₀ (ng/mL) J591-C 13.7 J591-E 25.4

Example 8 In Vivo ADC Efficacy Studies

Male severe combined immunodeficient mice (Fox Chase SCID®, C.B-17/Icr-Prkdcscid, Charles River) were nine weeks old with a body weight (BW) range of 18.9 to 26.7 grams on Day 1 of the study.

The 22Rv1 cells used for implantation were harvested during exponential growth and resuspended in 50% Matrigel (BD Biosciences) in phosphate buffered saline. On the day of tumor implant, each test mouse was injected subcutaneously in the right flank with 1×10⁷ cells (0.2 mL cell suspension), and tumor growth was monitored as the average size approached the target range of 100 to 150 mm³. Tumors were measured in two dimensions using calipers, and volume was calculated using the formula: Tumor Volume (mm³)=w ² ×l/2

where w=width and l=length, in mm, of the tumor. Tumor weight may be estimated with the assumption that 1 mg is equivalent to 1 mm³ of tumor volume.

Ten days after tumor implantation, designated as Day 1 of the study, the animals were sorted into groups each consisting of ten mice with individual tumor volumes ranging from 108 to 144 mm³ and group mean tumor volumes of 128 mm³.

All agents were administered intravenously (i.v.) via tail vein injection once per week for three weeks (qwk×3) or once on Day 1 (qd×1) in a dosing volume of 0.2 mL per 20 grams of body weight (10 mL/kg), scaled to the body weight of each individual animal. Tumors were measured using calipers twice per week, and each animal was euthanized when its tumor reached the endpoint volume of 1000 mm³ or at the end of the study (Day 114), whichever came first.

FIG. 1 shows the effect on mean tumour volume in groups of 10 miced dosed with J591-C at 0.3 (⋄—lower line) and 1.0 mg/kg (□) or J591-E at 0.3 (Δ) and 1.0 mg/kg (⋄—higher line) compared to vehicle (∘) control.

ABBREVIATIONS

-   Ac acetyl -   Acm acetamidomethyl -   Alloc allyloxycarbonyl -   Boc di-tert-butyl dicarbonate -   t-Bu tert-butyl -   Bzl benzyl, where Bzl-OMe is methoxybenzyl and Bzl-Me is     methylbenzene -   Cbz or Z benzyloxy-carbonyl, where Z—Cl and Z—Br are chloro- and     bromobenzyloxy carbonyl respectively -   DMF N,N-dimethylformamide -   Dnp dinitrophenyl -   DTT dithiothreitol -   Fmoc 9H-fluoren-9-ylmethoxycarbonyl -   imp N-10 imine protecting group:     3-(2-methoxyethoxy)propanoate-Val-Ala-PAB -   MC-OSu maleimidocaproyl-O—N-succinimide -   Moc methoxycarbonyl -   MP maleimidopropanamide -   Mtr 4-methoxy-2,3,6-trimethtylbenzenesulfonyl -   PAB para-aminobenzyloxycarbonyl -   PEG ethyleneoxy -   PNZ p-nitrobenzyl carbamate -   Psec 2-(phenylsulfonyl)ethoxycarbonyl -   TBDMS tert-butyldimethylsilyl -   TBDPS tert-butyldiphenylsilyl -   Teoc 2-(trimethylsilyl)ethoxycarbonyl -   Tos tosyl -   Troc 2,2,2-trichlorethoxycarbonyl chloride -   Trt trityl -   Xan xanthyl

SEQUENCES SEQ ID NO. 1 (J591 VH): EVQLQQSGPELKKPGTSVRISCKTSGYTFTEYTIHWVKQSHGKSLE WIGNINPNNGGTTYNQKFEDKATLTVDKSSSTAYMELRSLTSEDSA VYYCAAGWNFDYWGQGTTLTVSS SEQ ID NO. 2 (J591 VL): DIVMTQSHKFMSTSVGDRVSIICKASQDVGTAVDWYQQKPGQSPKL LIYWASTRHTGVPDRFTGSGSGTDFTLTITNVQSEDLADYFCQQYN SYPLTFGAGTMLDLK SEQ ID NO. 3 (J591 VH Delm): EVQLVQSGPEVKKPGATVKISCKTSGYTFTEYTIHWVKQAPGKGLE WIGNINPNNGGTTYNQKFEDKATLTVDKSTDTAYMELSSLRSEDTA VYYCAAGWNFDYWGQGTLLTVSS SEQ ID NO. 4 (J591 VK Delm): DIQMTQSPSSLSTSVGDRVTLTCKASQDVGTAVDWYQQKPGPSPKL LIYWASTRHTGIPSRFSGSGSGTDFTLTISSLQPEDFADYYCQQYN SYPLTFGPGTKVDIK SEQ ID NO. 5 (J415 VH): EVKLEESGGGLVQPGGSMKLSCVASGFTFSNYWMNWVRQSPEKGLE WVAEIRSQSNNFATHYAESVKGRVIISRDDSKSSVYLQMNNLRAED TGIYYCTRRWNNFWGQGTTLTVSS SEQ ID NO. 6 (J415 VL): NIVMTQFPKSMSISVGERVTLTCKASENVGTYVSWYQQKPEQSPKM LIYGASNRFTGVPDRFTGSGSATDFILTISSVQTEDLVDYYCGQSY TFPYTFGGGTKLEMK SEQ ID NO. 7 (J415-2 VH Delm): EVKLEESGGGLVQPGGSMKISCVASGFTFSNYWMNWVRQTPEKGLE WVALIRSQSNNFATHYAESVKGRVIISRDDSKSSVYLQMNSLRAED TAVYYCTRRWNNFWGQGTTVTVSS SEQ ID NO. 8 (J415-3 VH Delm): EVKLEESGGGLVQPGGSMKISCVASGFTFSNYWMNWVRQTPEKGLE WVAEIRSQSNNFATHYAESVKGRVIISRDDSKSSVYLQMNSLRAED TAVYYCTRRWNNFWGQGTTVTVSS SEQ ID NO. 9 (J415 VH Delm consensus): EVKLEESGGGLVQPGGSMKISCVASGFTFSNYWMNWVRQTPEKGLE WVAEIRSQSNNFATHYAESVKGRVIISRDDSKSSVYLQMNSLRAED TAVYYCTRRWNNFWGQGTTVTVSS SEQ ID NO. 10 (J415 VH-MuVH consensus): EVKLEESGGGLVQPGGSMKLSCVASGFTFSNYWMNWVRQSPEKGLE WVAEIRLQSDNFATHYAESVKGRVIISRDDSKSSVYLQMNNLRAED TGIYYCTTGGYGGRRSWNAFWGQGTLVTVSS SEQ ID NO. 11 (J415-2 VL Delm): NIVMTQSPKSMSASAGERMTLTCKASENVGTYVSWYQQKPTQSPKM LIYGASNRFTGVPDRFSGSGSGTDFILTASSVQAEDPVDYYCGQSY TFPYTFGGGTKLEMK SEQ ID NO. 12 (J415-3 VL Delm): NIVMTQSPKSMSASAGERMTLTCKASENVGTYVSWYQQKPTQSPKM LIYGASNRFTGVPDRFSGSGSGTDFILTASSVQAEDLVDYYCGQSY TFPYTFGGGTKLEMK SEQ ID NO. 13 (J415-4 VL Delm): NIVMTQSPKSMSASAGERMTLTCKASENVGTYVSWYQQKPTQSPKM LIYGASNRFTGVPDRFSGSGSGTDFILTISSVQAEDLVDYYCGQSY TFPYTFGGGTKLEMK SEQ ID NO. 14 (J415-6 VL Delm): NIVMTQFPKSMSASAGERMTLTCKASENVGTYVSWYQQKPEQSPKM LIYGASNRFTGVPDRFSGSGSGTDFILTISSVQAEDLVDYYCGQSY TFPYTFGGGTKLEMK SEQ ID NO. 15 (J415-7 VL Delm): NIVMTQFPKSMSASAGERVTLTCKASENVGTYVSWYQQKPTQSPKM LIYGASNRFTGVPDRFSGSGSGTDFILTISSVQAEDLVDYYCGQSY TFPYTFGGGTKLEMK SEQ ID NO. 16 (J415-8 VL Delm): NIVMTQFPKSMSASAGERMTLTCKASENSGTYVSWYQQKPEQSPKM LIYGASNRFTGVPDRFSGSGSGTDFILTISSVQAEDLVDYYCGQSY TFPYTFGGGTKLEMK SEQ ID NO. 17 (J415 VL consensus): NIVMTQFPKSMSASAGERMTLTCKASENVGTYVSWYQQKPTQSPKM LIYGASNRFTGVPDRFSGSGSGTDFILTISSVQAEDLVDYYCGQSY TFPYTFGGGTKLEMK SEQ ID NO. 18 (J415 VL-MuVL1 consensus): DIVMTQSPSSLAVSAGEKVTLSCKASESLLNVGNQKTYVAWYQQKP GQSPKLLIYGASTRESGVPDRFTGSGSGTDFILTISSVQAEDLAVY YCGNSYSFPLTFGGGTKLELK SEQ ID NO. 19 (J591 Delm heavy chain): EVQLVQSGPEVKKPGATVKISCKTSGYTFTEYTIHWVKQAPGKGLE WIGNINPNNGGTTYNQKFEDKATLTVDKSTDTAYMELSSLRSEDTA VYYCAAGWNFDYWGQGTLLTVSSASTKGPSVFPLAPSSKSTSGGTA ALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVV TVPSSSLGTQTYICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAP ELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWY VDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVS NKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLVK GFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSR WQQGNVFSCSVMHEALHNHYTQKSLSLSPGK SEQ ID NO. 20 (J591 Delm light chain): DIQMTQSPSSLSTSVGDRVTLTCKASQDVGTAVDWYQQKPGPSPKL LIYWASTRHTGIPSRFSGSGSGTDFTLTISSLQPEDFADYYCQQYN SYPLTFGPGTKVDIKRTVAAPSVFIFPPSDEQLKSGTASVVCLLNN FYPREAKVQWKVDNALQSGNSQESVTEQDSKDSTYSLSSTLTLSKA DYEKHKVYACEVTHQGLSSPVTKSFNRGEC 

The invention claimed is:
 1. A conjugate of formula ConjB:

 or ConjC

wherein: the drug loading is from 1 to 8; Ab is an antibody that binds to PSMA, the antibody comprising a VH domain having the sequence according to any one of SEQ ID NOs. 1, 3, 5, 7, 8, 9, or 10, optionally further comprising a VL domain having the sequence according to any one of SEQ ID NOs. 2, 4, 6, 11, 12, 13, 14, 15, 16, 17, or
 18. 2. The conjugate according to claim 1 wherein the antibody comprises a VH domain paired with a VL domain, the VH and VL domains having sequences selected from the group consisting of: SEQ ID NO. 1 paired with any one of SEQ ID NOs. 2, 4, 6, 11, 12, 13, 14, 15, 16, 17, or 18; SEQ ID NO. 3 paired with any one of SEQ ID NOs. 2, 4, 6, 11, 12, 13, 14, 15, 16, 17, or 18; SEQ ID NO. 5 paired with any one of SEQ ID NOs. 2, 4, 6, 11, 12, 13, 14, 15, 16, 17, or 18; SEQ ID NO. 7 paired with any one of SEQ ID NOs. 2, 4, 6, 11, 12, 13, 14, 15, 16, 17, or 18; SEQ ID NO. 8 paired with any one of SEQ ID NOs. 2, 4, 6, 11, 12, 13, 14, 15, 16, 17, or 18; SEQ ID NO. 9 paired with any one of SEQ ID NOs. 2, 4, 6, 11, 12, 13, 14, 15, 16, 17, or 18; or SEQ ID NO. 10 paired with any one of SEQ ID NOs. 2, 4, 6, 11, 12, 13, 14, 15, 16, 17, or
 18. 3. The conjugate according to claim 2 wherein the paired VH and VL domains have the sequences of: SEQ ID NO. 1 paired with SEQ ID NO. 2, SEQ ID NO. 3 paired with SEQ ID NO. 4, SEQ ID NO. 5 paired with SEQ ID NO. 6, SEQ ID NO. 7 paired with SEQ ID NO. 11, SEQ ID NO. 7 paired with SEQ ID NO. 12, SEQ ID NO. 7 paired with SEQ ID NO. 13, SEQ ID NO. 7 paired with SEQ ID NO. 14, SEQ ID NO. 7 paired with SEQ ID NO. 15, SEQ ID NO. 7 paired with SEQ ID NO. 16, SEQ ID NO. 7 paired with SEQ ID NO. 17, SEQ ID NO. 7 paired with SEQ ID NO. 18, SEQ ID NO. 8 paired with SEQ ID NO. 11, SEQ ID NO. 8 paired with SEQ ID NO. 12, SEQ ID NO. 8 paired with SEQ ID NO. 13, SEQ ID NO. 8 paired with SEQ ID NO. 14, SEQ ID NO. 8 paired with SEQ ID NO. 15, SEQ ID NO. 8 paired with SEQ ID NO. 16, SEQ ID NO. 8 paired with SEQ ID NO. 17, SEQ ID NO. 8 paired with SEQ ID NO. 18, SEQ ID NO. 9 paired with SEQ ID NO. 11, SEQ ID NO. 9 paired with SEQ ID NO. 12, SEQ ID NO. 9 paired with SEQ ID NO. 13, SEQ ID NO. 9 paired with SEQ ID NO. 14, SEQ ID NO. 9 paired with SEQ ID NO. 15, SEQ ID NO. 9 paired with SEQ ID NO. 16, SEQ ID NO. 9 paired with SEQ ID NO. 17, SEQ ID NO. 9 paired with SEQ ID NO. 18, SEQ ID NO. 10 paired with SEQ ID NO. 11, SEQ ID NO. 10 paired with SEQ ID NO. 12, SEQ ID NO. 10 paired with SEQ ID NO. 13, SEQ ID NO. 10 paired with SEQ ID NO. 14, SEQ ID NO. 10 paired with SEQ ID NO. 15, SEQ ID NO. 10 paired with SEQ ID NO. 16, SEQ ID NO. 10 paired with SEQ ID NO. 17, or SEQ ID NO. 10 paired with SEQ ID NO.
 18. 4. The conjugate according to claim 1 wherein the antibody in an intact antibody.
 5. The conjugate according to claim 1 wherein the antibody is humanised, deimmunised or resurfaced.
 6. The conjugate according to claim 1, wherein the drug loading is 1, 2, 3, or
 4. 7. A mixture of conjugates according to claim 1, wherein the average value of the drug loading is about 2 to about
 5. 8. A pharmaceutical composition comprising a therapeutically effective amount of the conjugate of claim 1 and a pharmaceutically acceptable diluent, carrier or excipient.
 9. The pharmaceutical composition of claim 8 further comprising a therapeutically effective amount of a chemotherapeutic agent.
 10. A method of treating prostate cancer comprising administering to a patient the pharmaceutical composition of claim
 8. 11. The method of claim 10 wherein the patient is administered a therapeutically effective amount of a chemotherapeutic agent, in combination with the conjugate. 